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U.S. Treasury Obligations Portfoliotrue
Semi-Annual Shareholder Report \| February 28, 2025

This semi-annual shareholder report contains important information about U.S. Treasury Obligations Portfolio for the period September 1, 2024, to February 28, 2025.
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.

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


Fund Name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment*^,†
U.S. Treasury Obligations Portfolio	$2	0.04%

*	Expense amounts may be voluntarily waived and/or reimbursed from time to time.

†	Annualized.

KEY FUND STATISTICS (as of February 28, 2025)


Total Net Assets	$477,820,657
Total Number of Portfolio Holdings	44

WHAT DID THE FUND INVEST IN? (as of February 28, 2025)

Portfolio Composition (% of Total Investments)

Schedule of Investments (unaudited)

February 28, 2025

U.S. Treasury Obligations Portfolio

(Percentages shown based on Portfolio net assets)

Security	Rate	Maturity Date	Face Amount	Value
Short-Term Investments — 100.9%
U.S. Treasury Bills — 26.9%
U.S. Treasury Bills	3.400%	3/4/25	$5,000,000	$4,998,169 (a)
U.S. Treasury Bills	3.987%	3/6/25	5,000,000	4,996,787 (a)
U.S. Treasury Bills	4.087%	3/13/25	10,000,000	9,985,742 (a)
U.S. Treasury Bills	4.278%	3/18/25	5,000,000	4,989,682 (a)
U.S. Treasury Bills	4.415%	4/1/25	10,000,000	9,962,197 (a)
U.S. Treasury Bills	4.290%	4/3/25	10,000,000	9,960,950 (a)
U.S. Treasury Bills	4.365%	4/8/25	5,000,000	4,977,226 (a)
U.S. Treasury Bills	4.338%	4/10/25	5,000,000	4,976,208 (a)
U.S. Treasury Bills	4.401%	4/24/25	5,000,000	4,967,656 (a)
U.S. Treasury Bills	4.425%	5/1/25	7,000,000	6,948,701 (a)
U.S. Treasury Bills	4.291%	5/6/25	15,000,000	14,884,758 (a)
U.S. Treasury Bills	4.366%	5/8/25	5,000,000	4,959,767 (a)
U.S. Treasury Bills	4.299%	5/13/25	15,000,000	14,872,554 (a)
U.S. Treasury Bills	4.472%	5/29/25	5,000,000	4,946,353 (a)
U.S. Treasury Bills	4.441%	6/5/25	7,500,000	7,413,900 (a)
U.S. Treasury Bills	4.338%	6/10/25	5,000,000	4,941,013 (a)
U.S. Treasury Bills	4.236%	7/1/25	5,000,000	4,930,583 (a)(b)
U.S. Treasury Bills	4.320%	7/24/25	5,000,000	4,916,122 (a)

Total U.S. Treasury Bills				128,628,368
U.S. Treasury Notes — 18.9%
U.S. Treasury Notes	3.875%	4/30/25	5,000,000	4,990,607
U.S. Treasury Notes (3 mo. U.S. Treasury Money Market Yield + 0.169%)	4.424%	4/30/25	5,000,000	4,999,601 (c)
U.S. Treasury Notes	4.625%	6/30/25	4,230,000	4,225,495
U.S. Treasury Notes (3 mo. U.S. Treasury Money Market Yield + 0.125%)	4.380%	7/31/25	5,000,000	4,998,819 (c)
U.S. Treasury Notes	5.000%	9/30/25	3,000,000	3,011,150
U.S. Treasury Notes	0.250%	10/31/25	2,500,000	2,432,770
U.S. Treasury Notes (3 mo. U.S. Treasury Money Market Yield + 0.170%)	4.425%	10/31/25	5,000,000	5,000,000 (c)
U.S. Treasury Notes	4.875%	11/30/25	1,550,000	1,555,454
U.S. Treasury Notes	0.375%	12/31/25	5,000,000	4,843,011
U.S. Treasury Notes	4.250%	12/31/25	5,000,000	4,999,545
U.S. Treasury Notes	3.875%	1/15/26	6,900,000	6,877,783
U.S. Treasury Notes (3 mo. U.S. Treasury Money Market Yield + 0.245%)	4.500%	1/31/26	10,000,000	10,006,352 (c)
U.S. Treasury Notes	1.625%	2/15/26	2,000,000	1,950,401
U.S. Treasury Notes	0.750%	3/31/26	3,000,000	2,892,106

See Notes to Financial Statements.

U.S. Treasury Obligations Portfolio 2025 Semi-Annual Report

Schedule of Investments (unaudited) (cont’d)

February 28, 2025

U.S. Treasury Obligations Portfolio

(Percentages shown based on Portfolio net assets)

Security	Rate	Maturity Date	Face Amount	Value
U.S. Treasury Notes — continued
U.S. Treasury Notes (3 mo. U.S. Treasury Money Market Yield + 0.150%)	4.405%	4/30/26	$10,000,000	$10,000,747 (c)
U.S. Treasury Notes (3 mo. U.S. Treasury Money Market Yield + 0.182%)	4.437%	7/31/26	5,000,000	4,994,409 (c)
U.S. Treasury Notes (3 mo. U.S. Treasury Money Market Yield + 0.205%)	4.460%	10/31/26	12,500,000	12,506,467 (c)

Total U.S. Treasury Notes				90,284,717
Repurchase Agreements — 55.1%
Canadian Imperial Bank of Commerce tri-party repurchase agreement dated 2/28/25; Proceeds at maturity — $5,001,813; (Fully collateralized by U.S. government obligations, 0.125% to 4.625% due 4/30/26 to 5/15/54; Market value — $5,101,860)	4.350%	3/3/25	5,000,000	5,000,000
Credit Agricole SA tri-party repurchase agreement dated 2/28/25; Proceeds at maturity — $40,014,500; (Fully collateralized by U.S. government obligations, 3.875% due 8/15/33; Market value — $40,800,062)	4.350%	3/3/25	40,000,000	40,000,000
Fixed Income Clearing Corp. tri-party repurchase agreement dated 2/28/25; Proceeds at maturity — $20,007,250; (Fully collateralized by U.S. government obligations, 4.375% due 5/15/34; Market value — $20,400,062)	4.350%	3/3/25	20,000,000	20,000,000
Fixed Income Clearing Corp. tri-party repurchase agreement dated 2/28/25; Proceeds at maturity — $18,447,700; (Fully collateralized by U.S. government obligations, 4.625% due 6/30/26; Market value — $18,809,974)	4.360%	3/3/25	18,441,000	18,441,000
HSBC Bank USA tri-party repurchase agreement dated 2/28/25; Proceeds at maturity — $25,008,979; (Fully collateralized by U.S. government obligations, 4.375% due 11/15/39; Market value — $25,509,197)	4.310%	3/3/25	25,000,000	25,000,000
ING Financial Markets LLC tri-party repurchase agreement dated 2/28/25; Proceeds at maturity — $5,001,813; (Fully collateralized by U.S. government obligations, 3.750% due 5/31/30; Market value — $5,100,033)	4.350%	3/3/25	5,000,000	5,000,000

See Notes to Financial Statements.

U.S. Treasury Obligations Portfolio 2025 Semi-Annual Report

U.S. Treasury Obligations Portfolio

(Percentages shown based on Portfolio net assets)

Security	Rate	Maturity Date	Face Amount	Value
Repurchase Agreements — continued
JPMorgan Securities LLC tri-party repurchase agreement dated 2/28/25; Proceeds at maturity — $60,021,800; (Fully collateralized by U.S. government obligations, 0.000% to 4.875% due 2/19/26 to 2/15/35; Market value — $61,222,242)	4.360%	3/3/25	$60,000,000	$60,000,000
Societe Generale NY tri-party repurchase agreement dated 2/28/25; Proceeds at maturity — $50,018,125; (Fully collateralized by U.S. government obligations, 4.625% due 2/15/40; Market value — $51,000,045)	4.350%	3/3/25	50,000,000	50,000,000
TD Securities LLC tri-party repurchase agreement dated 2/28/25; Proceeds at maturity — $40,014,567; (Fully collateralized by U.S. government obligations, 4.125% to 4.250% due 2/15/27 to 11/30/29; Market value — $40,800,062)	4.370%	3/3/25	40,000,000	40,000,000

Total Repurchase Agreements				263,441,000
Total Investments — 100.9% (Cost — $482,354,085#)				482,354,085
Liabilities in Excess of Other Assets — (0.9)%				(4,533,428 )
Total Net Assets — 100.0%				$477,820,657

#	Aggregate cost for federal income tax purposes is substantially the same.
(a)	Rate shown represents yield-to-maturity.
(b)	Securities traded on a when-issued or delayed delivery basis.
(c)	Variable rate security. Interest rate disclosed is as of the most recent information available. Certain variable rate securities are not based on a published reference rate and spread but are determined by the issuer or agent and are based on current market conditions. These securities do not indicate a reference rate and spread in their description above.

See Notes to Financial Statements.

U.S. Treasury Obligations Portfolio 2025 Semi-Annual Report

Statements of Changes in Net Assets

For the Six Months Ended February 28, 2025 (unaudited) and the Year Ended August 31, 2024	2025	2024
Operations:
Net investment income	$11,151,723	$26,747,374
Net realized gain	1,334	604
Increase in Net Assets From Operations	11,153,057	26,747,978
Capital Transactions:
Proceeds from contributions	412,124,470	1,202,683,204
Value of withdrawals	(400,438,779 )	(1,312,689,562 )
Increase (Decrease) in Net Assets From Capital Transactions	11,685,691	(110,006,358 )
Increase (Decrease) in Net Assets	22,838,748	(83,258,380 )
Net Assets:
Beginning of period	454,981,909	538,240,289
End of period	$477,820,657	$454,981,909

See Notes to Financial Statements.

U.S. Treasury Obligations Portfolio 2025 Semi-Annual Report

Financial Highlights

For the years ended August 31, unless otherwise noted:
	20251	2024	2023	2022	2021	2020
Net assets, end of period (millions)	$478	$455	$538	$401	$417	$985
Total return2	2.35 %	5.48 %	4.49 %	0.54 %	0.07 %	0.99 %
Ratios to average net assets:
Gross expenses	0.04 %3	0.04 %	0.04 %	0.04 %	0.03 %	0.03 %
Net expenses4	0.04 3	0.04	0.04	0.04	0.03	0.03 5
Net investment income	4.67 3	5.34	4.45	0.53	0.06	0.92

1	For the six months ended February 28, 2025 (unaudited).
2	Performance figures may reflect compensating balance arrangements, fee waivers and/or expense reimbursements. In the absence of compensating balance arrangements, fee waivers and/or expense reimbursements, the total return would have been lower. Past performance is no guarantee of future results. Total returns for periods of less than one year are not annualized.
3	Annualized.
4	The investment manager has voluntarily undertaken to limit Portfolio expenses. Such expense limitations may fluctuate daily and are voluntary and temporary and may be terminated by the investment manager at any time without notice.
5	Reflects fee waivers and/or expense reimbursements.

See Notes to Financial Statements.

U.S. Treasury Obligations Portfolio 2025 Semi-Annual Report

Notes to Financial Statements (unaudited)

1. Organization and significant accounting policies

U.S. Treasury Obligations Portfolio (the “Portfolio”) is a separate diversified investment series of Master Portfolio Trust (the “Trust”). The Trust, a Maryland statutory trust, is registered under the Investment Company Act of 1940, as amended (the “1940 Act”), as an open-end management investment company. The Declaration of Trust permits the Board of Trustees (the “Board”) to issue beneficial interests in the Portfolio. At February 28, 2025, all investors in the Portfolio were funds advised or administered by the investment manager of the Portfolio and/or its affiliates.

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

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

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

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

U.S. Treasury Obligations Portfolio 2025 Semi-Annual Report

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

•

Level 1 — unadjusted quoted prices in active markets for identical investments

•

Level 2 — other significant observable inputs (including quoted prices for similar investments, interest rates, prepayment speeds, credit risk, etc.)

•

Level 3 — significant unobservable inputs (including the Portfolio’s own assumptions in determining the fair value of investments)

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

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

ASSETS
Description	Quoted Prices (Level 1)	Other Significant Observable Inputs (Level 2)	Significant Unobservable Inputs (Level 3)	Total
Short-Term Investments†	—	$482,354,085	—	$482,354,085

†	See Schedule of Investments for additional detailed categorizations.

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

(c) Securities traded on a when-issued and delayed delivery basis. The Portfolio may trade securities on a when-issued or delayed delivery basis. In when-issued and

U.S. Treasury Obligations Portfolio 2025 Semi-Annual Report

Notes to Financial Statements (unaudited) (cont’d)

delayed delivery transactions, the securities are purchased or sold by the Portfolio with payment and delivery taking place in the future in order to secure what is considered to be an advantageous price and yield to the Portfolio at the time of entering into the transaction.

Purchasing such securities involves risk of loss if the value of the securities declines prior to settlement. These securities are subject to market fluctuations and their current value is determined in the same manner as for other securities.

(d) Interest income and expenses. Interest income (including interest income from payment-in-kind securities) consists of interest accrued and discount earned (including both original issue and market discount adjusted for amortization of premium) on the investments of the Portfolio. Expenses of the Portfolio are accrued daily. The Portfolio bears all costs of its operations other than expenses specifically assumed by the investment manager.

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

(f) Compensating balance arrangements. The Portfolio has an arrangement with its custodian bank whereby a portion of the custodian’s fees is paid indirectly by credits earned on the Portfolio’s cash on deposit with the bank.

(g) Income taxes. The Portfolio is classified as a partnership for federal income tax purposes. As such, each investor in the Portfolio is treated as owner of its proportionate share of the net assets, income, expenses and realized gains and losses of the Portfolio. Therefore, no federal income tax provision is required. It is intended that the Portfolio’s assets will be managed so an investor in the Portfolio can satisfy the requirements of Subchapter M of the Internal Revenue Code.

Management has analyzed the Portfolio’s tax positions taken on income tax returns for all open tax years and has concluded that as of August 31, 2024, no provision for income tax is required in the Portfolio’s financial statements. The Portfolio’s federal and state income tax returns for tax years for which the applicable statutes of limitations have not expired are subject to examination by the Internal Revenue Service and state departments of revenue.

(h) Other. Purchases, maturities and sales of money market instruments are accounted for on the date of the transaction. Realized gains and losses are calculated on the identified cost basis.

U.S. Treasury Obligations Portfolio 2025 Semi-Annual Report

2. Investment management agreement and other transactions with affiliates

Franklin Templeton Fund Adviser, LLC (“FTFA”) is the Portfolio’s investment manager and Western Asset Management Company, LLC (“Western Asset”) is the Portfolio’s subadviser. FTFA and Western Asset are indirect, wholly-owned subsidiaries of Franklin Resources, Inc. (“Franklin Resources”).

Under the investment management agreement, the Portfolio does not pay an investment management fee.

Expense amounts may be voluntarily waived and/or reimbursed from time to time.

FTFA is permitted to recapture amounts waived and/or reimbursed to the Portfolio during the same fiscal year under certain circumstances.

All officers and one Trustee of the Trust are employees of Franklin Resources or its affiliates and do not receive compensation from the Trust.

3. Derivative instruments and hedging activities

During the six months ended February 28, 2025, the Portfolio did not invest in derivative instruments.

4. Operating segments

The Portfolio has adopted the Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) 2023-07, Segment Reporting (Topic 280) - Improvements to Reportable Segment Disclosures. The update is limited to disclosure requirements and does not impact the Portfolio’s financial position or results of operations.

The Portfolio operates as a single operating segment, which is an investment portfolio. The Portfolio’s Investment Manager serves as the Chief Operating Decision Maker (CODM), evaluating fund-wide results and performance under a unified investment strategy. The CODM uses these measures to assess fund performance and allocate resources effectively. Internal reporting provided to the CODM aligns with the accounting policies and measurement principles used in the financial statements.

For information regarding segment assets, segment profit or loss, and significant expenses, refer to the Statement of Assets and Liabilities and the Statement of Operations, along with the related Notes to Financial Statements. The Portfolio’s Schedule of Investments provides details of the Portfolio’s investments that generate returns such as interest, dividends, and realized and unrealized gains or losses. Performance metrics, including expense ratios, are disclosed in the Financial Highlights.

U.S. Treasury Obligations Portfolio 2025 Semi-Annual Report

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

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

Pursuant to the requirements of the Securities Exchange Act 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, there unto duly authorized.

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

Assets:
Investments, at value	$218,913,085
Repurchase agreements, at value	263,441,000
Cash	963
Interest receivable	512,123
Total Assets	482,867,171
Liabilities:
Payable for securities purchased	4,930,583
Trustees’ fees payable	836
Accrued expenses	115,095
Total Liabilities	5,046,514
Total Net Assets	$477,820,657
Represented by:
Paid-in capital	$477,820,657

Investment Income:
Interest	$11,250,056
Expenses:
Fund accounting fees	31,049
Audit and tax fees	19,356
Legal fees	10,810
Trustees’ fees	5,911
Custody fees	648
Miscellaneous expenses	30,559
Total Expenses	98,333
Net Investment Income	11,151,723
Net Realized Gain on Investments	1,334
Increase in Net Assets From Operations	$11,153,057

Changes in and Disagreements with Accountants	For the period covered by this report
Not applicable.
Results of Meeting(s) of Shareholders	For the period covered by this report
Not applicable.
Remuneration Paid to Directors, Officers and Others	For the period covered by this report
Refer to the financial statements included herein.

Master Portfolio Trust

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

Date:	April 21, 2025

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

Date:	April 21, 2025


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

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

Date:	April 21, 2025