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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED

MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number 811-10407

Master Portfolio Trust

(Exact name of registrant as specified in charter)

One Madison Avenue, 17^th Floor, New York,\nNY 10010

(Address of principal executive offices) (Zip code)

Marc A. De Oliveira

Franklin Templeton

100 First Stamford Place

Stamford, CT 06902

(Name and address of agent for service)

Registrant’s telephone number, including area code:\n877-6LM-FUND/656-3863

Date of fiscal year end: August 31

Date of reporting period: August 31, 2026

\n \n \n \n

ITEM 1.

REPORT TO STOCKHOLDERS

(a) The Report to Shareholders is filed herewith

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

\n	\n
\n $\"image\"$ \n	\n $\"image\"$ \n
\n U.S. Treasury Reserves Portfolio\n \n
\n \n	\n Annual Shareholder Report \| August 31, 2026\n \n
\n $\"image\"$ \n	\n \n

This annual shareholder report contains important information about U.S. Treasury Reserves Portfolio for the period September 1, 2025, to August 31, 2026.
You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-masterfunds-documents. You can also request this information by contacting us at 1-800-625-4554, or 1-203-703-6002.\n

WHAT WERE THE FUND COSTS FOR THE LAST YEAR? (based on a hypothetical $10,000 investment)

\n \n

\n \n \n \n \n \n \n \n \n \n \n \n \n

\n	\n	\n
\n Fund Name \n	\n Costs of a $10,000 investment \n	\n Costs paid as a percentage of a $10,000 investment^*\n \n
\n U.S. Treasury Reserves Portfolio \n	\n $1 \n	\n 0.01% \n

\n \n \n \n \n

*	Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. Additional amounts may be voluntarily waived and/or reimbursed from time to time.

KEY FUND STATISTICS (as of August 31, 2026)

\n \n

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

\n	\n
\n Total Net Assets \n	\n $19,531,488,982 \n
\n Total Number of Portfolio Holdings \n	\n 62 \n
\n Total Management Fee Paid \n	\n $0 \n

WHAT DID THE FUND INVEST IN? (as of August 31, 2026)

Portfolio Composition (% of Total Investments)

$\"image\"$

\n \n \n \n \n \n \n \n \n \n \n \n \n

\n	\n
\n $\"image\"$ \n	\n WHERE CAN I FIND ADDITIONAL INFORMATION ABOUT THE FUND? \n
\n Additional information is available on https://www.franklintempleton.com/regulatory-masterfunds-documents, including its: \n
\n • proxy voting information • financial information • holdings • tax information \n

\n \n \n \n \n \n

U.S. Treasury Reserves Portfolio \n

PAGE 1 \n

98067-AHTSR-1026

\n true74.125.9\n

(b) Not applicable

\n \n \n \n

ITEM 2.

CODE OF ETHICS.

(a) The Registrant has adopted a code of ethics that applies to\nits principal executive officers and principal financial and accounting officer.

(d) N/A

(f) Pursuant to Item 19(a)(1), the Registrant is attaching as\nan exhibit a copy of its code of ethics that applies to its principal executive officers and principal financial and accounting officer.

\n \n \n \n

ITEM 3.

AUDIT COMMITTEE FINANCIAL EXPERT.

The Board of Trustees of the Registrant has determined\nthat Robert Abeles, Jr., possesses the technical attributes identified in Item 3 to Form N-CSR to qualify as an “audit committee\nfinancial expert,” and has designated Mr. Abeles, Jr. as the Audit Committee’s financial expert. Mr. Abeles, Jr. is an\n“independent” Trustee pursuant to paragraph (a)(2) of Item 3 to Form N-CSR.

Under applicable securities laws, a person determined to be an\naudit committee financial expert will not be deemed an “expert” for any purpose, including without limitation for the purposes\nof Section 11 of the Securities Act of 1933, as a result of being designated or identified as an audit committee financial expert. The\ndesignation or identification of a person as an audit committee financial expert does not impose on such person any duties, obligations,\nor liabilities greater than the duties, obligations, and liabilities imposed on such person as a member of the audit committee and board\nof directors in the absence of such designation or identification. The designation or identification of a person as an audit committee\nfinancial expert does not affect the duties, obligations, or liability of any other member of the audit committee or board of directors.

\n \n \n \n

ITEM 4.

PRINCIPAL ACCOUNTANT FEES AND SERVICES.

a) Audit Fees.\nThe aggregate fees billed in the last two fiscal years ending August 31, 2025 and August 31, 2026 (the “Reporting Periods”) for\nprofessional services rendered by the Registrant’s principal accountant (the “Auditor”) for the audit of the Registrant’s annual\nfinancial statements, or services that are normally provided by the Auditor in connection with the statutory and regulatory filings or\nengagements for the Reporting Periods, were $134,930 in August 31, 2025 and $136,279 in August 31, 2026.

b) Audit-Related Fees.\nThe aggregate fees billed in the Reporting Periods for assurance and related services by the Auditor that are reasonably related to the\nperformance of the Registrant’s financial statements were $0 in August 31, 2025 and $0 in August 31, 2026.

(c) Tax Fees. The\naggregate fees billed in the Reporting Periods for professional services rendered by the Auditor for tax compliance, tax advice and tax\nplanning (“Tax Services”) were $39,000 in August 31, 2025 and $39,000 in August 31, 2026. These services consisted of (i) review\nor preparation of U.S. federal, state, local and excise tax returns; (ii) U.S. federal, state and local tax planning, advice and assistance\nregarding statutory, regulatory or administrative developments, and (iii) tax advice regarding tax qualification matters and/or treatment\nof various financial instruments held or proposed to be acquired or held.

There were no fees billed for tax services by the Auditors to the\nRegistrant’s investment manager and any entity controlling, controlled by, or under common control with the investment manager that\nprovides ongoing services to the Registrant (“Service Affiliates”) during the Reporting Periods that required pre-approval\nby the Audit Committee.

d) All Other Fees.\nThe aggregate fees billed in the Reporting Periods for products and services provided by the Auditor to the Registrant, other than the\nservices reported in paragraphs (a) through (c) of this item, were $0 in August 31,\n2025 and $0 in August 31, 2026.

There were no other non-audit services rendered by the Auditor\nto the Service Affiliates requiring pre-approval by the Audit Committee in the Reporting Periods.

(e) Audit Committee’s pre–approval policies and procedures\ndescribed in paragraph (c)(7) of Rule 2-01 of Regulation S-X.

(1) The Charter for the Audit Committee (the “Committee”)\nof the Board of each registered investment company (the “Fund”) advised by the Registrant’s investment manager or one\nof their affiliates (each, an “Adviser”) requires that the Committee shall approve (a) all audit and permissible non-audit\nservices to be provided to the Fund and (b) all permissible non-audit services to be provided by the Fund’s independent auditors\nto the Adviser and any service providers controlling, controlled by or under common control with the Adviser that provide ongoing services\nto the Fund (“Covered Service Providers”) if the engagement relates directly to the operations and financial reporting of\nthe Fund. The Committee may implement policies and procedures by which such services are approved other than by the full Committee.

The Committee shall not approve non-audit services that the Committee\nbelieves may impair the independence of the auditors. As of the date of the approval of this Audit Committee Charter, permissible non-audit\nservices include any professional services (including tax services), that are not prohibited services as described below, provided to\nthe Fund by the independent auditors, other than those provided to the Fund in connection with an audit or a review of the financial statements\nof the Fund. Permissible non-audit services may not include: (i) bookkeeping or other services related to the accounting records or financial\nstatements of the Fund; (ii) financial information systems design and implementation; (iii) appraisal or valuation services, fairness\nopinions or contribution-in-kind reports; (iv) actuarial services; (v) internal audit outsourcing services; (vi) management functions\nor human resources; (vii) broker or dealer, investment adviser or investment banking services; (viii) legal services and expert services\nunrelated to the audit; and (ix) any other service the Public Company Accounting Oversight Board determines, by regulation, is impermissible.

Pre-approval by the Committee of any permissible non-audit services\nis not required so long as: (i) the aggregate amount of all such permissible non-audit services provided to the Fund, the Adviser and\nthe Covered Service Providers constitutes not more than 5% of the total amount of revenues paid to the independent auditors during the\nfiscal year in which the permissible non-audit services are provided to (a) the Fund, (b) the Adviser and (c) any entity controlling,\ncontrolled by or under common control with the Adviser that provides ongoing services to the Fund during the fiscal year in which the\nservices are provided that would have to be approved by the Committee; (ii) the permissible non-audit services were not recognized by\nthe Fund at the time of the engagement to be non-audit services; and (iii) such services are promptly brought to the attention of the\nCommittee and approved by the Committee (or its delegate(s)) prior to the completion of the audit.

(2) None of the services described in paragraphs (b) through (d)\nof this Item were performed in reliance on paragraph (c)(7)(i)(C) of Rule 2-01 of Regulation S-X.

(f) Not applicable.

(g) Non-audit fees billed by the Auditor for services rendered\nto the Registrant and the Service Affiliates during the reporting period were $334,889 in August 31, 2025 and $344,935 in August 31, 2026.

(h) Yes. The Registrant’s Audit Committee has considered\nwhether the provision of non-audit services that were rendered to Service Affiliates, which were not pre-approved (not requiring pre-approval),\nis compatible with maintaining the Auditor's independence. All services provided by the Auditor to the Registrant or to the Service Affiliates,\nwhich were required to be pre-approved, were pre-approved as required.

(i) Not applicable.

(j) Not applicable.

\n \n \n \n

ITEM 5.

AUDIT COMMITTEE OF LISTED REGISTRANTS.

Not applicable.

\n \n \n \n

ITEM 6.

SCHEDULE OF INVESTMENTS.

\n \n \n \n

(a)

Please see the schedule of investments contained in the Financial\n Statements and Financial Highlights included under Item 7 of this Form N-CSR.

\n \n \n \n

(b)

Not applicable.

\n \n \n \n

ITEM 7.

FINANCIAL STATEMENTS AND FINANCIAL HIGHLIGHTS FOR OPEN-END MANAGEMENT INVESTMENT COMPANIES.

Schedule\nof Investments\n\n

August 31, 2026

U.S.\nTreasury Reserves Portfolio

(Percentages shown\nbased on Portfolio net assets)

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

\n Security \n	\n \n	\n Rate \n	\n Maturity\n \n Date \n	\n Face\n \n Amount \n	\n Value \n
\n Short-Term\n Investments — 102.6%
\n U.S.\n Treasury Bills — 76.1%
\n U.S.\n Treasury Bills	\n 0.000% \n	\n 9/1/26 \n	\n $778,900,000 \n	\n $778,900,000 \n (a) \n
\n U.S.\n Treasury Bills	\n 2.488% \n	\n 9/3/26 \n	\n 620,030,000 \n	\n 619,904,783 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.275% \n	\n 9/8/26 \n	\n 672,255,000 \n	\n 671,780,338 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.407% \n	\n 9/10/26 \n	\n 900,000,000 \n	\n 899,174,250 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.494% \n	\n 9/15/26 \n	\n 654,600,000 \n	\n 653,676,711 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.537% \n	\n 9/17/26 \n	\n 699,000,000 \n	\n 697,869,173 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.670% \n	\n 9/22/26 \n	\n 1,197,000,000 \n	\n 1,194,402,691 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.654% \n	\n 9/24/26 \n	\n 413,000,000 \n	\n 412,026,630 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.658% \n	\n 9/29/26 \n	\n 850,000,000 \n	\n 847,577,173 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.695% \n	\n 10/1/26 \n	\n 800,000,000 \n	\n 797,538,333 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.695% \n	\n 10/6/26 \n	\n 725,000,000 \n	\n 722,410,438 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.753% \n	\n 10/8/26 \n	\n 647,600,000 \n	\n 645,120,830 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.704% \n	\n 10/13/26 \n	\n 520,000,000 \n	\n 517,776,567 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.793% \n	\n 10/15/26 \n	\n 475,520,000 \n	\n 473,342,734 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.714% \n	\n 10/20/26 \n	\n 399,000,000 \n	\n 397,011,987 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.789% \n	\n 10/22/26 \n	\n 501,000,000 \n	\n 498,352,633 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.838% \n	\n 10/27/26 \n	\n 135,000,000 \n	\n 134,208,300 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.870% \n	\n 10/29/26 \n	\n 517,000,000 \n	\n 513,836,741 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.873% \n	\n 11/3/26 \n	\n 115,000,000 \n	\n 114,236,366 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.829% \n	\n 11/5/26 \n	\n 375,000,000 \n	\n 372,460,937 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.790% \n	\n 11/12/26 \n	\n 422,640,000 \n	\n 419,506,879 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.835% \n	\n 11/17/26 \n	\n 62,000,000 \n	\n 61,503,371 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.779% \n	\n 11/19/26 \n	\n 400,000,000 \n	\n 396,761,001 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.958% \n	\n 11/24/26 \n	\n 75,000,000 \n	\n 74,325,025 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.802% \n	\n 11/27/26 \n	\n 350,000,000 \n	\n 346,865,583 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.944% \n	\n 12/1/26 \n	\n 107,500,000 \n	\n 106,457,007 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.785% \n	\n 12/3/26 \n	\n 350,000,000 \n	\n 346,667,688 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.877% \n	\n 12/8/26 \n	\n 150,000,000 \n	\n 148,460,583 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.836% \n	\n 12/15/26 \n	\n 250,000,000 \n	\n 247,282,031 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.787% \n	\n 12/17/26 \n	\n 128,500,000 \n	\n 127,094,496 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.863% \n	\n 12/22/26 \n	\n 75,800,000 \n	\n 74,915,667 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.963% \n	\n 12/31/26 \n	\n 75,000,000 \n	\n 74,032,000 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.967% \n	\n 1/21/27 \n	\n 100,000,000 \n	\n 98,487,305 \n (a) \n
\n U.S.\n Treasury Bills	\n 4.049% \n	\n 1/28/27 \n	\n 50,000,000 \n	\n 49,191,054 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.994% \n	\n 2/4/27 \n	\n 100,000,000 \n	\n 98,329,500 \n (a) \n
\n U.S.\n Treasury Bills	\n 3.941% \n	\n 2/11/27 \n	\n 227,082,500 \n	\n 223,172,646 \n (a) \n
\n \n
\n Total\n U.S. Treasury Bills	\n 14,854,659,451 \n

See\nNotes to Financial Statements.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

Schedule\nof Investments (cont’d)\n\n

August 31, 2026

U.S.\nTreasury Reserves Portfolio

(Percentages shown\nbased on Portfolio net assets)

\n Security \n	\n \n	\n Rate \n	\n Maturity \n Date \n	\n Face \n Amount \n	\n Value \n
\n U.S.\n Treasury Notes — 26.5%
\n U.S.\n Treasury Notes	\n 3.500% \n	\n 9/30/26 \n	\n $100,000,000 \n	\n $99,983,994 \n \n
\n U.S.\n Treasury Notes	\n 4.625% \n	\n 10/15/26 \n	\n 100,000,000 \n	\n 100,115,980 \n \n
\n U.S.\n Treasury Notes (3 mo. U.S. Treasury \n Money\n Market Yield + 0.205%)	\n 4.011% \n	\n 10/31/26 \n	\n 552,500,000 \n	\n 552,560,477 \n (b) \n
\n U.S.\n Treasury Notes	\n 1.250% \n	\n 11/30/26 \n	\n 50,000,000 \n	\n 49,702,918 \n \n
\n U.S.\n Treasury Notes	\n 1.625% \n	\n 11/30/26 \n	\n 52,000,000 \n	\n 51,754,995 \n \n
\n U.S.\n Treasury Notes	\n 4.250% \n	\n 11/30/26 \n	\n 104,500,000 \n	\n 104,670,440 \n \n
\n U.S.\n Treasury Notes	\n 1.250% \n	\n 12/31/26 \n	\n 90,000,000 \n	\n 89,337,913 \n \n
\n U.S.\n Treasury Notes	\n 4.250% \n	\n 12/31/26 \n	\n 92,000,000 \n	\n 92,207,720 \n \n
\n U.S.\n Treasury Notes (3 mo. U.S. Treasury \n Money\n Market Yield + 0.098%)	\n 3.904% \n	\n 1/31/27 \n	\n 363,000,000 \n	\n 363,050,217 \n (b) \n
\n U.S.\n Treasury Notes	\n 4.125% \n	\n 1/31/27 \n	\n 55,000,000 \n	\n 55,118,318 \n \n
\n U.S.\n Treasury Notes	\n 1.125% \n	\n 2/28/27 \n	\n 35,000,000 \n	\n 34,586,079 \n \n
\n U.S.\n Treasury Notes	\n 1.875% \n	\n 2/28/27 \n	\n 74,800,000 \n	\n 74,182,839 \n \n
\n U.S.\n Treasury Notes	\n 4.125% \n	\n 2/28/27 \n	\n 34,000,000 \n	\n 34,093,173 \n \n
\n U.S.\n Treasury Notes	\n 4.250% \n	\n 3/15/27 \n	\n 63,660,000 \n	\n 63,902,944 \n \n
\n U.S.\n Treasury Notes	\n 2.500% \n	\n 3/31/27 \n	\n 86,050,000 \n	\n 85,509,451 \n \n
\n U.S.\n Treasury Notes	\n 3.875% \n	\n 3/31/27 \n	\n 154,600,000 \n	\n 154,810,840 \n \n
\n U.S.\n Treasury Notes	\n 4.500% \n	\n 4/15/27 \n	\n 82,000,000 \n	\n 82,428,652 \n \n
\n U.S.\n Treasury Notes	\n 2.750% \n	\n 4/30/27 \n	\n 36,500,000 \n	\n 36,271,649 \n \n
\n U.S.\n Treasury Notes	\n 3.750% \n	\n 4/30/27 \n	\n 131,600,000 \n	\n 131,595,343 \n \n
\n U.S.\n Treasury Notes (3 mo. U.S. Treasury \n Money\n Market Yield + 0.160%)	\n 3.966% \n	\n 4/30/27 \n	\n 716,700,000 \n	\n 716,834,860 \n (b) \n
\n U.S.\n Treasury Notes	\n 0.500% \n	\n 5/31/27 \n	\n 53,000,000 \n	\n 51,740,918 \n \n
\n U.S.\n Treasury Notes	\n 2.625% \n	\n 5/31/27 \n	\n 150,000,000 \n	\n 148,731,989 \n \n
\n U.S.\n Treasury Notes (3 mo. U.S. Treasury \n Money\n Market Yield + 0.159%)	\n 3.965% \n	\n 7/31/27 \n	\n 669,000,000 \n	\n 669,306,370 \n (b) \n
\n U.S.\n Treasury Notes (3 mo. U.S. Treasury \n Money\n Market Yield + 0.190%)	\n 3.996% \n	\n 10/31/27 \n	\n 967,700,000 \n	\n 968,710,451 \n (b) \n
\n U.S.\n Treasury Notes (3 mo. U.S. Treasury \n Money\n Market Yield + 0.099%)	\n 3.905% \n	\n 1/31/28 \n	\n 150,000,000 \n	\n 150,022,437 \n (b) \n
\n U.S.\n Treasury Notes (3 mo. U.S. Treasury \n Money\n Market Yield + 0.103%)	\n 3.909% \n	\n 4/30/28 \n	\n 225,000,000 \n	\n 225,207,315 \n (b) \n
\n \n
\n Total\n U.S. Treasury Notes	\n 5,186,438,282 \n
\n Total\n Investments — 102.6% (Cost — $20,041,097,733#)	\n 20,041,097,733 \n
\n Liabilities\n in Excess of Other Assets — (2.6)%	\n (509,608,751 \n ) \n
\n Total\n Net Assets — 100.0%	\n $19,531,488,982 \n

See\nNotes to Financial Statements.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

U.S.\nTreasury Reserves Portfolio

\n \n \n \n \n \n \n \n \n \n

Aggregate\n cost for federal income tax purposes is substantially the same.

(a)

Rate\n shown represents yield-to-maturity.

(b)

Variable\n rate security. Interest rate disclosed is as of the most recent information available. Certain variable rate

securities\n are not based on a published reference rate and spread but are determined by the issuer or agent and

are\n based on current market conditions. These securities do not indicate a reference rate and spread in their

description\n above.

See\nNotes to Financial Statements.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

Statement\nof Assets and Liabilities\n\n

August 31, 2026

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

\n Assets: \n	\n
\n Investments,\n at value	\n $20,041,097,733 \n
\n Cash \n	\n 501,755,284 \n
\n Interest\n receivable	\n 27,749,410 \n
\n Prepaid\n expenses	\n 25,600 \n
\n Total\n Assets	\n 20,570,628,027 \n
\n Liabilities: \n	\n
\n Payable\n for securities purchased	\n 1,038,778,879 \n
\n Trustees’\n fees payable	\n 3,240 \n
\n Accrued\n expenses	\n 356,926 \n
\n Total\n Liabilities	\n 1,039,139,045 \n
\n Total\n Net Assets	\n $19,531,488,982 \n
\n Represented\n by:	\n
\n Paid-in\n capital	\n $19,531,488,982 \n

See\nNotes to Financial Statements.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

Statement\nof Operations \n\n

For the Year Ended August 31,\n2026

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

\n Investment\n Income:	\n
\n Interest \n	\n $696,694,518 \n
\n Expenses: \n	\n
\n Investment\n management fee (Note\n 2)	\n 18,228,214 \n
\n Trustees’\n fees	\n 488,165 \n
\n Legal\n fees	\n 445,927 \n
\n Fund\n accounting fees	\n 236,584 \n
\n Custody\n fees	\n 107,436 \n
\n Audit\n and tax fees	\n 32,177 \n
\n Miscellaneous\n expenses	\n 122,460 \n
\n Total\n Expenses	\n 19,660,963 \n
\n Less:\n Fee waivers and/or expense reimbursements (Note 2)	\n (18,228,214 \n ) \n
\n Net\n Expenses	\n 1,432,749 \n
\n Net\n Investment Income	\n 695,261,769 \n
\n Net\n Realized Gain on Investments\n	\n 188,587 \n
\n Increase\n in Net Assets From Operations	\n $695,450,356 \n

See\nNotes to Financial Statements.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

Statements\nof Changes in Net Assets

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

\n For\n the Years Ended August 31,	\n 2026 \n	\n 2025 \n
\n Operations: \n	\n	\n
\n Net\n investment income\n	\n $695,261,769 \n	\n $822,742,149 \n
\n Net\n realized gain \n	\n 188,587 \n	\n 251,822 \n
\n Increase\n in Net Assets From Operations	\n 695,450,356 \n	\n 822,993,971 \n
\n Capital\n Transactions:	\n	\n
\n Proceeds\n from contributions	\n 80,845,613,340 \n	\n 73,211,157,941 \n
\n Value\n of withdrawals	\n (79,347,097,819 \n ) \n	\n (73,708,113,214 \n ) \n
\n Increase\n (Decrease) in Net Assets From Capital \n Transactions \n	\n 1,498,515,521 \n	\n (496,955,273 \n ) \n
\n Increase\n in Net Assets	\n 2,193,965,877 \n	\n 326,038,698 \n
\n Net\n Assets:	\n	\n
\n Beginning\n of year	\n 17,337,523,105 \n	\n 17,011,484,407 \n
\n End\n of year	\n $19,531,488,982 \n	\n $17,337,523,105 \n

See\nNotes to Financial Statements.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

Financial\nHighlights

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

\n For\n the years ended August 31:\n
\n \n	\n 2026 \n	\n 2025 \n	\n 2024 \n	\n 2023 \n	\n 2022 \n
\n Net\n assets, end of year (millions)	\n $19,531 \n	\n $17,338 \n	\n $17,011 \n	\n $15,171 \n	\n $17,407 \n
\n Total\n return1\n	\n 3.89 \n % \n	\n 4.61 \n % \n	\n 5.52 \n % \n	\n 4.42 \n % \n	\n 0.52 \n % \n
\n Ratios\n to average net assets:
\n Gross\n expenses	\n 0.11 \n % \n	\n 0.11 \n % \n	\n 0.11 \n % \n	\n 0.11 \n % \n	\n 0.11 \n % \n
\n Net\n expenses2,3\n	\n 0.01 \n	\n 0.01 \n	\n 0.01 \n	\n 0.01 \n	\n 0.01 \n
\n Net\n investment income	\n 3.81 \n	\n 4.51 \n	\n 5.38 \n	\n 4.32 \n	\n 0.46 \n

\n \n \n \n \n \n \n \n \n \n

Performance\n figures may reflect compensating balance arrangements, fee waivers and/or expense reimbursements.

In\n the absence of compensating balance arrangements, fee waivers and/or expense reimbursements, the total

return\n would have been lower. Past performance is no guarantee of future results.\n

The\n investment manager, pursuant to the terms of the feeder fund’s investment management agreement, has

agreed\n to waive 0.10% of Portfolio expenses, attributable to the Portfolio’s investment management fee.

Additional\n amounts may be voluntarily waived and/or reimbursed from time to time.\n

Reflects\n fee waivers and/or expense reimbursements.

See\nNotes to Financial Statements.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

Notes\nto Financial Statements

1. Organization\nand significant accounting policies\n

U.S. Treasury Reserves Portfolio\n(the “Portfolio”) is a separate diversified investment series of\nMaster Portfolio Trust (the “Trust”). The Trust, a Maryland statutory trust, is registered under\nthe Investment Company Act of 1940, as amended (the “1940 Act”), as an open-end management\ninvestment company. The Declaration of Trust permits the Board of Trustees (the\n“Board”) to\nissue beneficial interests in the Portfolio. At August 31, 2026, all investors in\nthe Portfolio were funds advised or administered by the investment manager of the Portfolio\nand/or its affiliates.

The Portfolio follows the accounting\nand reporting guidance in Financial Accounting Standards\nBoard (“FASB”)\nAccounting Standards Codification Topic 946, Financial Services –\nInvestment Companies (“ASC\n946”).\nThe following are significant accounting policies consistently\nfollowed by the Portfolio and are in conformity with U.S. generally accepted accounting\nprinciples (“GAAP”), including, but not limited to, ASC 946. Estimates and assumptions\nare required to be made regarding assets, liabilities and changes in net assets resulting\nfrom operations when financial statements are prepared. Changes in the economic environment,\nfinancial markets and any other parameters used in determining these estimates\ncould cause actual results to differ. Subsequent events have been evaluated through\nthe date the financial statements were issued.

(a) Investment\nvaluation. In\naccordance with Rule 2a-7 under the 1940 Act, money market\ninstruments are valued at amortized cost, which approximates market value. This method\ninvolves valuing portfolio securities at their cost and thereafter assuming a constant\namortization to maturity of any discount or premium. The Portfolio’s use of amortized\ncost is subject to its compliance with certain conditions as specified by Rule 2a-7 under\nthe 1940 Act.

Pursuant to policies adopted by\nthe Board, the Portfolio’s manager has been designated as the\nvaluation designee and is responsible for the oversight of the daily valuation process. The\nPortfolio’s manager is assisted by the Global Fund Valuation Committee (the “Valuation\nCommittee”).\nThe Valuation Committee is responsible for making fair value determinations, evaluating\nthe effectiveness of the Portfolio’s pricing policies, and reporting to the Board.

The Portfolio uses valuation techniques\nto measure fair value that are consistent with the market\napproach and/or income approach, depending on the type of security and the particular\ncircumstance. The market approach uses prices and other relevant information generated\nby market transactions involving identical or comparable securities. The income approach\nuses valuation techniques to discount estimated future cash flows to present value.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

GAAP establishes\na disclosure hierarchy that categorizes the inputs to valuation techniques used\nto value assets and liabilities at measurement date. These inputs are summarized in the\nthree broad levels listed below:

•

Level\n1 — unadjusted quoted prices in active markets for identical investments\n

•

Level\n2 — other significant observable inputs (including quoted prices for similar investments,\ninterest rates, prepayment speeds, credit risk, etc.)\n

•

Level\n3 — significant unobservable inputs (including the Portfolio’s own assumptions in determining\nthe fair value of investments)

The inputs or methodologies used\nto value securities are not necessarily an indication of the\nrisk associated with investing in those securities.

The following is a summary of the\ninputs used in valuing the Portfolio’s assets carried at fair value:\n

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

ASSETS

Description

Quoted\n Prices

(Level\n 1)

Other\n Significant

Observable\n Inputs

(Level\n 2)

Significant\n

Unobservable\n

Inputs\n

(Level\n 3)

Total

Short-Term\n Investments†

—

$20,041,097,733

—

$20,041,097,733

\n \n \n \n

†

See\n Schedule of Investments for additional detailed categorizations.

(b) Repurchase\nagreements. The\nPortfolio may enter into repurchase agreements with institutions\nthat its subadviser has determined are creditworthy. Each repurchase agreement\nis recorded at cost. Under the terms of a typical repurchase agreement, the Portfolio\nacquires a debt security subject to an obligation of the seller to repurchase, and of the\nPortfolio to resell, the security at an agreed-upon price and time, thereby determining the\nyield during the Portfolio’s holding period. When entering into repurchase agreements, it is\nthe Portfolio’s policy that its custodian or a third party custodian, acting on the Portfolio’s behalf,\ntake possession of the underlying collateral securities, the market value of which, at all\ntimes, at least equals the principal amount of the repurchase transaction, including accrued\ninterest. To the extent that any repurchase transaction maturity exceeds one business\nday, the value of the collateral is marked-to-market and measured against the value\nof the agreement in an effort to ensure the adequacy of the collateral. If the counterparty\ndefaults, the Portfolio generally has the right to use the collateral to satisfy the\nterms of the repurchase transaction. However, if the market value of the collateral declines\nduring the period in which the Portfolio seeks to assert its rights or if bankruptcy proceedings\nare commenced with respect to the seller of the security, realization of the collateral\nby the Portfolio may be delayed or limited.\n

(c) Interest\nincome and expenses. Interest\nincome (including interest income from payment-in-kind\nsecurities) consists of interest accrued and discount earned (including both original\nissue and market discount adjusted for amortization of premium) on the

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

Notes\nto Financial Statements (cont’d)

investments\nof the Portfolio. Expenses of the Portfolio are accrued daily. The Portfolio bears all\ncosts of its operations other than expenses specifically assumed by the investment manager.

(d) Method\nof allocation. Net\ninvestment income of the Portfolio is allocated pro rata, based\non respective ownership interests, among the Fund and other investors in the Portfolio\n(the “Holders”) at the time of such determination. Gross realized gains and/or losses\nof the Portfolio are allocated to the Holders in a manner such that the net asset values\nper share of each Holder, after each such allocation, is closer to the total of all Holders’\nnet asset values divided by the aggregate number of shares outstanding for all Holders.

(e) Income\ntaxes. The\nPortfolio is classified as a partnership for federal income tax purposes.\nAs such, each investor in the Portfolio is treated as owner of its proportionate share\nof the net assets, income, expenses and realized gains and losses of the Portfolio. Therefore,\nno federal income tax provision is required. It is intended that the Portfolio’s assets\nwill be managed so an investor in the Portfolio can satisfy the requirements of Subchapter\nM of the Internal Revenue Code.

Management has analyzed the Portfolio’s\ntax positions taken on income tax returns for all open\ntax years and has concluded that as of August 31, 2026, no provision for income tax is required\nin the Portfolio’s financial statements. The Portfolio’s federal and state income tax returns\nfor the prior three fiscal years are subject to examination by the Internal Revenue Service\nand state departments of revenue.

(f) Other. Purchases,\nmaturities and sales of money market instruments are accounted for on\nthe date of the transaction. Realized gains and losses are calculated on the identified cost\nbasis.

2. Investment\nmanagement agreement and other transactions with affiliates

Franklin Templeton Fund Adviser,\nLLC (“FTFA”)\nis the Portfolio’s investment manager and Western\nAsset Management Company, LLC (“Western Asset”) is the Portfolio’s subadviser. FTFA\nand Western Asset are indirect, wholly-owned subsidiaries of Franklin Templeton, Inc. (“Franklin\nTempleton”) (prior to August 17, 2026, known as Franklin Resources, Inc.).

Under the investment management\nagreement, the Portfolio pays an investment management\nfee, calculated daily and paid monthly, at an annual rate of 0.10% of the Portfolio’s\naverage daily net assets.

FTFA provides administrative and\ncertain oversight services to the Portfolio. FTFA delegates to\nthe subadviser the day-to-day portfolio management of the Portfolio. For its services, FTFA\npays Western Asset a fee monthly, at an annual rate equal to 70% of the net management\nfee it receives from the Portfolio.\n

As a result of the investment management\nagreement between FTFA and the feeder fund, FTFA has agreed\nto waive 0.10% of Portfolio expenses, attributable to the Portfolio’s

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

investment management\nfee. Additional amounts may be voluntarily waived and/or reimbursed\nfrom time to time.

During the year ended August 31,\n2026, fees waived and/or expenses reimbursed amounted to\n$18,228,214.

FTFA is permitted to recapture amounts\nwaived and/or reimbursed to the Portfolio during the same\nfiscal year under certain circumstances.

All officers and one Trustee of\nthe Trust are employees of Franklin Templeton or its affiliates and\ndo not receive compensation from the Trust.\n

3. Derivative\ninstruments and hedging activities

During the year ended August 31,\n2026, the Portfolio did not invest in derivative instruments.

4. Operating\nsegments

The Portfolio operates as a single\noperating segment, which is an investment portfolio. A management\ngroup assigned to the Portfolio within the Portfolio’s investment manager serves\nas the Chief Operating Decision Maker (“CODM”) and is responsible for evaluating the\nPortfolio’s operating results and allocating resources in accordance with the Portfolio’s investment\nstrategy. Internal reporting provided to the CODM aligns with the accounting policies\nand measurement principles used in the financial statements.

For information regarding segment\nassets, segment profit or loss, and significant expenses, refer\nto the Statement of Assets and Liabilities and the Statement of Operations, along with the\nrelated Notes to Financial Statements. The Portfolio’s Schedule of Investments provide details\nof the Portfolio’s investments that generate returns such as interest, dividends, and realized\ngains or losses. Performance metrics, including expense ratios, are disclosed in the Financial\nHighlights.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

Report\nof Independent Registered Public Accounting Firm

To the Board of Trustees of\nMaster Portfolio Trust and Investors of U.S. Treasury Reserves Portfolio

Opinion on the Financial Statements

We have audited the accompanying\nstatement of assets and liabilities, including the schedule of investments,\nof U.S. Treasury Reserves Portfolio (one of the portfolios constituting Master Portfolio Trust, referred\nto hereafter as the “Portfolio”)\nas of August 31, 2026, the related statement of operations for the year\nended August 31, 2026, the statement of changes in net assets for each of the two years in the period\nended August 31, 2026, including the related notes, and the financial highlights for each of the five years\nin the period ended August 31, 2026 (collectively referred to as the “financial statements”). In our opinion,\nthe financial statements present fairly, in all material respects, the financial position of the Portfolio\nas of August 31, 2026, the results of its operations for the year then ended, the changes in its net\nassets for each of the two years in the period ended August 31, 2026 and the financial highlights for each\nof the five years in the period ended August 31, 2026 in conformity with accounting principles generally\naccepted in the United States of America.

Basis for Opinion

These financial statements are the\nresponsibility of the Portfolio’s management. Our responsibility is to express\nan opinion on the Portfolio’s financial statements based on our audits. We are a public accounting\nfirm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and\nare required to be independent with respect to the Portfolio in accordance with the relevant ethical requirements\nrelating to our audit, which include standards of the American Institute of Certified Public Accountants\n(AICPA) Code of Professional Conduct, as well as U.S. federal securities laws and the applicable\nrules and regulations of the Securities and Exchange Commission.\n

We conducted our audits of these\nfinancial statements in accordance with the auditing standards of the PCAOB\nand in accordance with auditing standards generally accepted in the United States of America. Those\nstandards require that we plan and perform the audit to obtain reasonable assurance about whether\nthe financial statements are free of material misstatement, whether due to error or fraud.\n

Our audits included performing procedures\nto assess the risks of material misstatement of the financial statements,\nwhether due to error or fraud, and performing procedures that respond to those risks. Such procedures\nincluded examining, on a test basis, evidence regarding the amounts and disclosures in the financial\nstatements. Our audits also included evaluating the accounting principles used and significant estimates\nmade by management, as well as evaluating the overall presentation of the financial statements.\nOur procedures included confirmation of securities owned as of August 31, 2026 by correspondence\nwith the custodian and brokers; when replies were not received from brokers, we performed\nother auditing procedures. We believe that our audits provide a reasonable basis for our opinion.

/s/ PricewaterhouseCoopers LLP

Baltimore,\nMaryland
October 22, 2026

We have served as the auditor of\none or more investment companies in the Franklin Templeton Group of Funds\nsince 1948.

U.S.\nTreasury Reserves Portfolio 2026 Annual Report

Board\nApproval of Management and \n\n

Subadvisory Agreements (unaudited)

The Executive\nand Contracts Committee of the Board of Trustees (the “Executive and Contracts\nCommittee”) considered the Management Agreement between the Trust and Franklin\nTempleton Fund Adviser, LLC (“FTFA”) with respect to the Fund and the subadvisory agreement\nbetween FTFA and Western Asset Management Company, LLC (“Western Asset” or\nthe “Subadviser”, and together with FTFA, the “Advisers”) with respect to the Fund (collectively,\nthe “Agreements”) at a meeting held on April 22, 2026. At an in-person meeting\nheld on May 19, 2026, the Executive and Contracts Committee reported to the full Board\nof Trustees their considerations and recommendation with respect to the Agreements,\nand the Board of Trustees, including a majority of the Independent Trustees, considered\nand approved renewal of the Agreements.

In arriving at their decision to\napprove the renewal of the Agreements, the Trustees met with\nrepresentatives of the Advisers, including relevant investment advisory personnel; considered\na variety of information prepared by the Advisers, materials provided by Broadridge\nand advice and materials provided by counsel to the Independent Trustees; reviewed\nperformance and expense information for peer groups of comparable funds selected\nby Broadridge (the “Performance Universe”) and certain other comparable products available\nfrom Western Asset or affiliates of Western Asset, including separate accounts managed\nby Western Asset; and requested and reviewed additional information as necessary.\nThese reviews were in addition to information obtained by the Trustees at their regular\nquarterly meetings (and various committee meetings) with respect to the Fund’s performance\nand other relevant matters and related discussions with the Advisers’ personnel.\nThe information received and considered by the Board both in conjunction with the\nMay meeting and at prior meetings was both written and oral. With respect to the Broadridge\nmaterials, the Board was provided with a description of the methodology used to\ndetermine the similarity of the Fund with the funds included in the Performance Universe. It\nwas noted that while the Board found the Broadridge data generally useful they recognized\nits limitations, including that the data may vary depending on the end date selected\nand that the results of the performance comparisons may vary depending on the selection\nof the peer group and its composition over time. The Board noted that the Fund is a\n“master fund” in a “master-feeder” structure, in which each feeder fund has the same investment\nobjective and policies as the Fund and invests substantially all of its assets in the\nFund. The information provided and presentations made to the Board encompassed the Fund\nand all funds for which the Board has responsibility, including the following feeder funds\nin the Fund (each, a “Feeder Fund”): Western Asset Institutional U.S. Treasury Reserves,\na series of Legg Mason Partners Institutional Trust, and Western Asset Premier Institutional\nU.S. Treasury Reserves, a series of Legg Mason Partners Institutional Trust.

As part of their review, the Trustees\nexamined FTFA’s ability to provide high quality oversight\nand administrative and shareholder support services to the Fund and the Subadvisers’\nability to provide high quality investment management services to the Fund.

U.S.\nTreasury Reserves Portfolio

Board\nApproval of Management and \n\n

Subadvisory Agreements (unaudited) (cont’d)

The Trustees\nconsidered the experience of FTFA’s personnel in providing the types of services\nthat FTFA is responsible for providing to the Fund; the ability of FTFA to attract and retain\ncapable personnel; and the capability and integrity of FTFA’s senior management and staff.\nThe Trustees also considered the investment philosophy and research and decision-making\nprocesses of the Subadviser; the experience of their key advisory personnel responsible\nfor management of the Fund; the ability of the Subadviser to attract and retain capable\nresearch and advisory personnel; the risks to the Advisers associated with sponsoring\nthe Fund (such as entrepreneurial, operational, reputational, litigation and regulatory\nrisk), as well as FTFA’s and the Subadviser’s risk management processes; the capability\nand integrity of the Advisers’ senior management and staff; and the level of skill required\nto manage the Fund. In addition, the Trustees reviewed the quality of the Advisers’ services\nwith respect to regulatory compliance and compliance with the investment policies of\nthe Fund, and conditions that might affect the Advisers’ ability to provide high quality services\nto the Fund in the future, including their business reputations, financial conditions and\noperational stabilities. The Board also considered the policies and practices of FTFA and\nthe Subadviser regarding the selection of brokers and dealers and the execution of portfolio\ntransactions. Based on the foregoing, the Trustees concluded that the Subadviser’s investment\nprocess, research capabilities and philosophy were well suited to the Fund given\nits investment objectives and policies, and that the Advisers would be able to meet any\nreasonably foreseeable obligations under the Agreements.

The Board reviewed the qualifications,\nbackgrounds and responsibilities of FTFA’s and Western\nAsset’s senior personnel and the team of investment professionals primarily responsible\nfor the day-to-day portfolio management of the Fund. The Board also considered,\nbased on its knowledge of FTFA and its affiliates, the financial resources of Franklin\nTempleton, Inc. (prior to August 17, 2026, known as Franklin Resources, Inc.), the parent\norganization of the Advisers. The Board recognized the importance of having a fund manager\nwith significant resources.

In considering the performance of\nthe Fund, the Board received and considered performance information\nfor each Feeder Fund as well as for the Performance Universe selected by Broadridge.\nThe Board noted that the Feeder Funds’ performance was the same as the performance\nof the Fund (except for the effect of fees at the Feeder Fund level), and therefore\nwas relevant to the Board’s consideration of the Fund’s performance. The Board was\nprovided with a description of the methodology used to determine the similarity of the Feeder\nFunds with the funds included in the Performance Universe. It was noted that while the\nBoard found the Broadridge data generally useful they recognized its limitations, including\nthat the data may vary depending on the end date selected and that the results of the\nperformance comparisons may vary depending on the selection of the peer group and its composition\nover time. The Board also noted that it had received and discussed with management\ninformation throughout the year at periodic intervals comparing each Feeder

U.S.\nTreasury Reserves Portfolio

Fund’s\nperformance against its benchmark and against each Feeder Fund’s peers. In addition,\nthe Board considered each Feeder Fund’s performance in light of overall financial market\nconditions.

• The\ninformation comparing Western Asset Institutional U.S. Treasury Reserves’ performance\nto that of its Performance Universe, consisting of all funds (including the Feeder\nFund) classified as institutional U.S. Treasury money market funds by Broadridge, showed,\namong other data, that the Feeder Fund’s performance for the 1-, 3-, 5- and 10-year\nperiods ended December 31, 2025 was above the median.

• The\ninformation comparing Western Asset Premier Institutional U.S. Treasury Reserves’ performance\nto that of its Performance Universe, consisting of all funds (including the Feeder\nFund) classified as institutional U.S. Treasury money market funds by Broadridge, showed,\namong other data, that the Feeder Fund’s performance for the 1-, 3- and 5-year and\nsince inception periods ended December 31, 2025 was above the median.

The Trustees also considered the\nmanagement fee payable by the Fund to FTFA, total expenses\npayable by the Fund and the fee that FTFA pays to the Subadviser. They reviewed information\nconcerning management fees paid to investment advisers of similarly managed funds\nas well as fees paid by Western Asset’s other clients, including separate accounts managed\nby Western Asset. The Trustees also noted that the Fund does not pay any management\nfees directly to the Subadviser because FTFA pays the Subadviser for services provided\nto the Fund out of the management fee FTFA receives from the Fund.

• The\ninformation comparing Western Asset Institutional U.S. Treasury Reserves’ Contractual\nand Actual Management Fees as well as its actual total expense ratio to its expense\ngroup, consisting of a group of institutional U.S. Treasury money market funds (including\nthe Feeder Fund) chosen by Broadridge to be comparable to the Feeder Fund, showed\nthat the Feeder Fund’s Contractual Management Fee and Actual Management Fee\nwere above the median. The Board noted that the Feeder Fund’s actual total expense ratio\nwas equal to the median. The Board also considered that the current limitation on the\nFeeder Fund’s expenses is expected to continue through December 2026.

• The\ninformation comparing Western Asset Premier Institutional U.S. Treasury Reserves’ Contractual\nand Actual Management Fees as well as its actual total expense ratio to its expense\ngroup, consisting of a group of institutional U.S. Treasury money market funds (including\nthe Feeder Fund) chosen by Broadridge to be comparable to the Feeder Fund, showed\nthat the Feeder Fund’s Contractual Management Fee and Actual Management Fee\nwere above the median. The Board noted that the Feeder Fund’s actual total expense ratio\nwas below the median. The Board also considered that the current limitation on the Feeder\nFund’s expenses is expected to continue through December 2026.

U.S.\nTreasury Reserves Portfolio

Board\nApproval of Management and \n\n

Subadvisory Agreements (unaudited) (cont’d)

The Trustees\nfurther evaluated the benefits of the advisory relationship to the Advisers, including,\namong others, the profitability of the relationship to the Advisers; the direct and indirect\nbenefits that the Advisers may receive from their relationships with the Fund, including\nthe “fallout benefits,” such as reputational value derived from serving as investment\nadviser to the Fund; and the affiliation between the Advisers and certain other service\nproviders for the Fund. In that connection, the Board considered that the ancillary benefits\nthat the Advisers receive were reasonable. The Trustees noted that Western Asset does\nnot have soft dollar arrangements.

Finally, the Trustees considered,\nin light of the profitability information provided by the Advisers,\nthe extent to which economies of scale would be realized by the Advisers as the assets\nof the Fund grow. The Trustees considered an analysis of the profitability of FTFA and its\naffiliates in providing services to the Fund and the Feeder Fund.

• The\nBoard noted that the Western Asset Institutional U.S. Treasury Reserves’ Contractual Management\nFee and Actual Management Fee were above the median of the peer group.\nThe Board also noted the size of the Feeder Fund.

• The\nBoard noted that the Western Asset Premier Institutional U.S. Treasury Reserves’ Contractual\nManagement Fee and Actual Management Fee were above the median of the\npeer group. The Board also noted the size of the Feeder Fund.

In their deliberations with respect\nto these matters, the Independent Trustees were advised by\ntheir independent counsel, who is independent, within the meaning of the Securities and Exchange\nCommission rules regarding the independence of counsel, of the Advisers. The Independent\nTrustees weighed the foregoing matters in light of the advice given to them by their\nindependent counsel as to the law applicable to the review of investment advisory contracts.\nIn arriving at a decision, the Trustees, including the Independent Trustees, did not identify\nany single matter as all-important or controlling, and each Trustee may have attributed\ndifferent weight to the various factors in evaluating the Agreements. The foregoing\nsummary does not detail all the matters considered. The Trustees judged the terms\nand conditions of the Agreements, including the investment advisory fees, in light of all\nof the surrounding circumstances.

Based upon their review, the Trustees,\nincluding all of the Independent Trustees, determined,\nin the exercise of their business judgment, that they were generally satisfied with\nthe quality of investment advisory services being provided by the Advisers but would continue\nto closely monitor the Advisers’ performance; that the fees to be paid to the Advisers\nunder the Agreements were fair and reasonable given the scope and quality of the services\nrendered by the Advisers; and that approval of the Agreements was in the best interest\nof the Fund and its shareholders.

U.S.\nTreasury Reserves Portfolio

\n \n \n \n

ITEM 8.

CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS FOR OPEN-END MANAGEMENT INVESTMENT COMPANIES.

The information is disclosed as part of the Financial Statements\nincluded in Item 7 of this Form N-CSR.

\n \n \n \n

ITEM 9.

PROXY DISCLOSURES FOR OPEN-END MANAGEMENT INVESTMENT COMPANIES.

The information is disclosed as part of the Financial Statements\nincluded in Item 7 of this Form N-CSR.

\n \n \n \n

ITEM 10.

REMUNERATION PAID TO DIRECTORS, OFFICERS, AND OTHERS OF OPEN-END MANAGEMENT INVESTMENT COMPANIES.

The information is disclosed as part of the Financial Statements\nincluded in Item 7 of this Form N-CSR.

\n \n \n \n

ITEM 11.

STATEMENT REGARDING BASIS FOR APPROVAL OF INVESTMENT ADVISORY CONTRACT.

The information is disclosed as part of the Financial Statements\nincluded in Item 7 of this Form N-CSR, as applicable.

\n \n \n \n

ITEM 12.

DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable.

\n \n \n \n

ITEM 13.

PORTFOLIO MANAGERS OF CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable.

\n \n \n \n

ITEM 14.

PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT INVESTMENT COMPANY AND AFFILIATED PURCHASERS.

Not applicable.

\n \n \n \n

ITEM 15.

SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

There have been no changes to the procedures by which shareholders\nmay recommend nominees to the Registrant’s Board of Trustees that would require disclosure herein.

\n \n \n \n

ITEM 16.

CONTROLS AND PROCEDURES.

\n \n \n \n

(a)

The Registrants acknowledge the Staff’s comment. In future filings on Form N-CSR,\n the certifications required by Rule 30a-2 and Item 19(a)(3) will include the designations “principal executive officer” and “principal\n financial officer” in the signature blocks, reflecting the capacity in which each signatory executes the certification, in conformity\n with the language of the Rule and Form N-CSR. The Registrants may also include each signatory’s actual title with respect to the Funds\n alongside the required designation

\n \n \n \n

(b)

There were no changes in the Registrant’s internal control over financial\n reporting (as defined in Rule 30a-3(d) under the 1940 Act) that occurred during the period covered by this report that have materially\n affected or are likely to materially affect the Registrant’s internal control over financial reporting.

\n \n \n \n

ITEM 17.

DISCLOSURE OF SECURITIES LENDING ACTIVITIES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable.

\n \n \n \n

ITEM 18.

RECOVERY OF ERRONEOUSLY AWARDED COMPENSATION.

\n \n \n \n

(a)

Not applicable.

\n \n \n \n

(b)

Not applicable.

\n \n \n \n

ITEM 19.

EXHIBITS.

(a) (1) Code\nof Ethics attached hereto.

Exhibit 99.CODE ETH

(a) (3) Certifications\npursuant to section 302 of the Sarbanes-Oxley Act of 2002 attached hereto.

Exhibit 99.CERT

(b) Certifications\npursuant to Section 906 of the Sarbanes-Oxley Act of 2002 attached hereto.

Exhibit 99.906CERT

SIGNATURES

Pursuant to the requirements of the Securities Exchange\nAct of 1934 and the Investment Company Act of 1940, the registrant has duly caused this Report to be signed on its behalf by the undersigned,\nthereunto duly authorized.

Master Portfolio Trust

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

By:	/s/ Jane Trust
	Jane Trust
	Chief Executive Officer

Date:	October 28, 2026

Pursuant to the requirements of the Securities Exchange\nAct of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant\nand in the capacities and on the dates indicated.

\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n

By:	/s/ Jane Trust
	Jane Trust
	Chief Executive Officer

Date:	October 28, 2026

By:	/s/ Christopher Berarducci
	Christopher Berarducci
	Principal Financial Officer

Date:	October 28, 2026

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