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: 811-07332 and 811-08162

Name and address of agent for service: John M. Perlowski, Chief Executive Officer, BlackRock Funds III and Master Investment Portfolio, 55 East 52^nd Street, New York, NY 10055

Registrants’ telephone number, including area code: (800) 537-4942

Date of fiscal year end: 12/31/2022

Date of reporting period: 06/30/2022

Item 1 – Report to Stockholders

(a) The Report to Shareholders is attached herewith.

BlackRock Funds III

·  BlackRock Cash Funds: Institutional

·  BlackRock Cash Funds: Treasury

Table of Contents

Money Market Overview For the 6-Month Period Ended June 30, 2022

Market Review

During the six-month period ended June 30, 2022, monetary accommodation was removed at an accelerated pace and a strong disparity between supply and demand at the front-end of the market continued. The United States saw inflation increase at its fastest pace in four decades throughout the period, with the Consumer Price Index (“CPI”) increasing 9.1% on an annualized basis in June 2022. During its meeting on March 16th, the Federal Open Market Committee (the “FOMC”, or “the Committee”) raised the range for the Federal Funds target rate - for the first time since December 2018 – from 0.00% - 0.25% to 0.25% - 0.50%.

Responding to increasing inflation at home, the FOMC raised the Federal Funds target rate at each meeting during the second quarter. The Committee elected to increase the Federal Funds target rate by 0.50% at its May 2022 meeting, and another 0.75% at its June 2022 meeting, bringing the target rate to 1.50% - 1.75% as of June 30, 2022. In a statement released in conjunction with the June 15th FOMC meeting, the Committee reiterated that it is “highly attentive to inflation risks,” and added that it is “strongly committed to returning inflation to its 2.00% objective.”

According to the updated “dot plot” median Federal Funds rate forecast accompanying the June 2022 meeting, the FOMC penciled in an additional 1.50% of rate hikes for 2022 relative to the March 2022 dot plot, bringing the median projection to 3.40%. The June “dot plot” also showed the median Federal Funds rate topping out at 3.80% in 2023, reflecting an additional 1.00% of rate hikes relative to the March 2022 projections. Also, an easing of monetary policy is forecasted for 2024, with the median Federal Funds rate projected to decline to 3.40%.

The Fed median economic growth forecasts declined relative to the March 2022 projections, while the median core inflation projections for 2022 and 2023 moved higher. Projected median unemployment levels also moved higher over the forecast horizon. Net new U.S. Treasury bill (“T-bill”) supply contracted $246.1 billion during the period, further exacerbating the supply and demand imbalance in the money market space and resulting in a distorted yield curve at the end of the period. T-bill tenors between 1-month and 1-year dramatically rose despite this dynamic as markets priced in several rate hikes during the first half of the year. Yields on the 1-month and 12-month T-bills rose by 1.00% and 2.40%, respectively, to 1.02% and 2.78% on June 30, 2022.

As the large unevenness between supply and demand persisted throughout the period, daily utilization of the Fed’s overnight reverse repurchase agreement program (“RRP”) continued to climb, peaking at $2.33 trillion in late June 2022. A defensive posture by investors arguably contributed to softness in rates on repurchase agreements (“repo”) during the period. The secured overnight financing rate (“SOFR”) — a broad measure of the cost of borrowing cash overnight collateralized by Treasury securities — regularly printed below the lower bound of the range for the Federal Funds beginning in early May 2022. Industry-wide money market mutual funds (“MMFs”) experienced net outflows of $228 billion during the six-month period ended June 30, 2022. Of this, assets of government and prime MMFs fell by $232 billion and $13 billion, respectively, while assets municipal MMFs grew by nearly $17 billion.

Outlook

An outlook for persistently elevated inflation suggests increases in the target range for the Federal Funds rate by the FOMC of at least 0.50% are possible at the next few FOMC meetings. Forecasts by the FOMC and futures contracts for Federal Funds suggest that monetary policy could become restrictive later this year. Defensive positioning by investors and insufficient supply of T-bills and similar investments will likely contribute to generally depressed levels on repurchase agreements and elevated usage of the Fed’s RRP facility by eligible counterparties.

Past performance is not an indication of future results. Index performance is shown for illustrative purposes only. You cannot invest directly in an index.

Investment Objective

BlackRock Cash Funds: Institutional’s (the “Fund”) investment objective is to seek a high level of income consistent with liquidity and the preservation of capital.

CURRENT SEVEN-DAY YIELDS

The 7-Day SEC Yields may differ from the 7-Day Yields shown due to the fact that the 7-Day SEC Yields exclude distributed capital gains.

Expense Example

See “Disclosure of Expenses” for further information on how expenses were calculated.

Past performance is not an indication of future results.

Investment Objective

BlackRock Cash Funds: Treasury’s (the “Fund”) investment objective is to seek current income as is consistent with liquidity and stability of principal.

CURRENT SEVEN-DAY YIELDS

The 7-Day SEC Yields may differ from the 7-Day Yields shown due to the fact that the 7-Day SEC Yields exclude distributed capital gains.

Expense Example

See “Disclosure of Expenses” for further information on how expenses were calculated.

Past performance is not an indication of future results.

Shareholders of each Fund may incur the following charges: (a) transactional expenses; and (b) operating expenses, including administration fees, service and distribution fees, and other fund expenses. The expense examples shown (which are based on a hypothetical investment of $1,000 invested at the beginning of the period and held through the end of the period) are intended to assist shareholders both in calculating expenses based on an investment in each Fund and in comparing these expenses with similar costs of investing in other mutual funds.

The expense examples provide information about actual account values and actual expenses. Annualized expense ratios reflect contractual and voluntary fee waivers, if any. In order to estimate the expenses a shareholder paid during the period covered by this report, shareholders can divide their account value by $1,000 and then multiply the result by the number corresponding to their Fund and share class under the heading entitled “Expenses Paid During the Period.”

The expense examples also provide information about hypothetical account values and hypothetical expenses based on a Fund’s actual expense ratio and an assumed rate of return of 5% per year before expenses. In order to assist shareholders in comparing the ongoing expenses of investing in these Funds and other funds, compare the 5% hypothetical examples with the 5% hypothetical examples that appear in shareholder reports of other funds.

The expenses shown in the expense examples are intended to highlight shareholders’ ongoing costs only and do not reflect transactional expenses, such as sales charges, if any. Therefore, the hypothetical examples are useful in comparing ongoing expenses only and will not help shareholders determine the relative total expenses of owning different funds. If these transactional expenses were included, shareholder expenses would have been higher.

Statements of Assets and Liabilities (unaudited)

June 30, 2022

See notes to financial statements.

Statements of Operations (unaudited)

Six Months Ended June 30, 2022

See notes to financial statements.

Statements of Changes in Net Assets

See notes to financial statements.

Financial Highlights

(For a share outstanding throughout each period)

See notes to financial statements.

Financial Highlights (continued)

(For a share outstanding throughout each period)

See notes to financial statements.

Financial Highlights (continued)

(For a share outstanding throughout each period)

See notes to financial statements.

Notes to Financial Statements (unaudited)

BlackRock Funds III (the “Trust”) is registered under the Investment Company Act of 1940, as amended (the “1940 Act”), as an open-end management investment company. The Trust is organized as a Delaware statutory trust. The following, each of which is a series of the Trust, are referred to herein collectively as the “Funds” or individually as a “Fund”:

Each Fund seeks to achieve its investment objective by investing all of its assets in a corresponding series of Master Investment Portfolio (“MIP”): Money Market Master Portfolio and Treasury Money Market Master Portfolio (each, a “Master Portfolio” and together, the “Master Portfolios”). MIP is an affiliate of the Trust. Each Master Portfolio has the same investment objective and strategies as its corresponding Fund. The value of each Fund’s investment in its corresponding Master Portfolio reflects the Fund’s proportionate interest in the net assets of the Master Portfolio. The performance of each Fund is directly affected by the performance of the Master Portfolios. At June 30, 2022, the percentage of each Master Portfolio owned by its corresponding Fund was as follows: Institutional owned 100% of Money Market Master Portfolio and Treasury owned 91.4% of Treasury Money Market Master Portfolio. The financial statements of the Master Portfolios, including the Schedules of Investments, are included elsewhere in this report and should be read in conjunction with the Funds’ financial statements.

Institutional only offers SL Agency Shares and is only available for certain eligible investors. Treasury offers multiple classes of shares. Institutional, Select, SL Agency, Capital, Premium and Trust Shares are sold without a sales charge and only to certain eligible investors. All classes of shares have identical voting, dividend, liquidation and other rights and are subject to the same terms and conditions, and differ principally with respect to administration fees.

The Board of Trustees of the Trust and Board of Trustees of MIP are referred to throughout this report as the “Board” and the members are referred to as “Trustees”.

Treasury operates as a “government money market fund” under Rule 2a-7 under the 1940 Act. The Fund is not subject to liquidity fees or temporary suspensions of redemptions due to declines in the Fund’s weekly liquid assets.

Institutional prices and transacts its shares at a net asset value (“NAV”) per share calculated to four decimal places, reflecting market-based values of its portfolio holdings (i.e., at a “floating” NAV).

With respect to Institutional, the Board is permitted to impose a liquidity fee of up to 2% on the value of shares redeemed or temporarily restrict redemptions from Institutional for up to 10 business days during a 90 day period, in the event that Institutional’s weekly liquid assets fall below certain thresholds.

The Funds, together with certain other registered investment companies advised by BlackRock Fund Advisors (“BFA” or the “Manager”) or its affiliates, are included in a complex of open-end equity, multi-asset, index and money market funds referred to as the BlackRock Multi-Asset Complex.

The financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”), which may require management to make estimates and assumptions that affect the reported amounts of assets and liabilities in the financial statements, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates. Each Fund is considered an investment company under U.S. GAAP and follows the accounting and reporting guidance applicable to investment companies. Below is a summary of significant accounting policies:

Investment Transactions and Income Recognition: For financial reporting purposes, contributions to and withdrawals from each Master Portfolio are accounted for on a trade date basis. The Funds record their proportionate share of the Master Portfolio’s income, expenses and realized and unrealized gains and losses on a daily basis. In addition, the Funds accrue their own expenses. Income, expenses and realized and unrealized gains and losses are allocated daily to each class based on its relative net assets.

Distributions: Distributions from net investment income are declared daily and paid monthly. Distributions of capital gains are distributed at least annually and are recorded on the ex-dividend dates. The character and timing of distributions are determined in accordance with U.S. federal income tax regulations, which may differ from U.S. GAAP.

Liquidity Fees: Any liquidity fees imposed on the value of shares redeemed in the event that Institutional’s weekly liquid assets fall below certain thresholds are recorded as paid-in-capital. The liquidity fees are collected and retained by Institutional for the benefit of Institutional’s remaining interest holders.

Indemnifications: In the normal course of business, a Fund enters into contracts that contain a variety of representations that provide general indemnification. A Fund’s maximum exposure under these arrangements is unknown because it involves future potential claims against a Fund, which cannot be predicted with any certainty.

Other: Expenses directly related to a Fund or its classes are charged to that Fund or the applicable class. Expenses directly related to the Funds and other shared expenses prorated to the Funds are allocated daily to each class based on their relative net assets or other appropriate methods. Other operating expenses shared by several funds, including other funds managed by the BlackRock Advisors, LLC (the “Administrator”), are prorated among those funds on the basis of relative net assets or other appropriate methods.

Notes to Financial Statements (unaudited) (continued)

Investment Valuation Policies: Each Fund’s policy is to value its financial instruments at fair value. Each Fund records its investment in the Master Portfolio at fair value based on the Funds’ proportionate interest in the net assets of the Master Portfolio. Valuation of securities held by the Master Portfolio is discussed in Note 3 of the Master Portfolio’s Notes to Financial Statements, which are included elsewhere in this report.

Administration: The Trust, on behalf of the Funds, entered into an Administration Agreement with the Administrator, which has agreed to provide general administrative services (other than investment advice and related portfolio activities). The Administrator has agreed to bear all of the Funds’ ordinary operating expenses, excluding, generally, investment advisory fees, distribution fees, brokerage and other expenses related to the execution of portfolio transactions, extraordinary expenses and certain other expenses which are borne by the Funds. The Administrator is entitled to receive for these administrative services an annual fee based on the average daily net assets of each Fund as follows:

From time to time, the Administrator may waive such fees in whole or in part. Any such waiver will reduce the expenses of the Funds and, accordingly, have a favorable impact on their performance. The Administrator may delegate certain of its administration duties to sub-administrators.

For the six months ended June 30, 2022, the following table shows the class specific administration fees borne directly by each share class of each Fund:

As of June 30, 2022, the only investors for the SL Agency Shares of Institutional are investment companies for which (i) BFA, BlackRock Institutional Trust Company, N.A. (“BTC”), or an affiliate provides investment advisory or administration services, or (ii) BTC acts as securities lending agent and which have directed BTC on their behalf to invest securities lending cash collateral in SL Agency Shares of Institutional. Affiliated shareholders in the SL Agency Shares of the Funds represent a significant portion of the outstanding shares and net assets of Institutional and Treasury.

Distribution Fees: The Trust, on behalf of the Funds, entered into a Distribution Agreement with BlackRock Investments, LLC (“BRIL”), an affiliate of the Administrator. Shareholders of Capital, Institutional, Premium, Select, SL Agency and Trust Shares of the Funds do not pay any fees for distribution services.

Expense Waivers and Reimbursements: The Administrator contractually agreed to waive a portion of its administration fees for the Select Shares of Treasury through June 30, 2023. After giving effect to such contractual expense waiver, the administration fees for the Select Shares of Treasury will be 0.13%.

The fees and expenses of the Fund’s trustees who are not “interested persons” of the Trust, as defined in the 1940 Act (“Independent Trustees”), counsel to the Independent Trustees and the Funds’ independent registered public accounting firm (together, the “independent expenses”) are paid directly by the Funds. The Administrator has contractually agreed to reimburse the Funds or provide an offsetting credit against the administration fees paid by the Funds in an amount equal to these independent expenses through June 30, 2023. These amounts are included in fees waived and/or reimbursed by the Administrator in the Statements of Operations. For the six months ended June 30, 2022, the amounts waived were as follows:

The Administrator has also voluntarily agreed to waive and/or reimburse a portion of their respective administration fees to enable the Fund to maintain minimum levels of daily net investment income if applicable. These amounts, if any, are reported in the Statement of Operations as fees waived and/or reimbursed by the Administrator. The Administrator may discontinue the waiver and/or reimbursement at any time. With respect to Treasury, for the six months ended June 30, 2022, the amounts waived and/or reimbursed was $248,193.

Interfund Lending: In accordance with an exemptive order (the “Order”) from the U.S. Securities and Exchange Commission (“SEC”), each Fund may participate in a joint lending and borrowing facility for temporary purposes (the “Interfund Lending Program”), subject to compliance with the terms and conditions of the Order, and to the extent permitted by each Fund’s investment policies and restrictions. Each Fund is currently permitted to borrow and lend under the Interfund Lending Program.

A lending BlackRock fund may lend in aggregate up to 15% of its net assets but may not lend more than 5% of its net assets to any one borrowing fund through the Interfund Lending Program. A borrowing BlackRock fund may not borrow through the Interfund Lending Program or from any other source more than 33 1/3% of its total assets (or any lower threshold provided for by the fund’s investment restrictions). If a borrowing BlackRock fund’s total outstanding borrowings exceed 10% of its total assets, each of its outstanding interfund loans will be subject to collateralization of at least 102% of the outstanding principal value of the loan. All interfund loans are for temporary or emergency purposes and the interest rate to be charged will be the average of the highest current overnight repurchase agreement rate available to a lending fund and the bank loan rate, as calculated according to a formula established by the Board.

Notes to Financial Statements (unaudited) (continued)

During the period ended June 30, 2022, the Funds did not participate in the Interfund Lending Program.

Trustees and Officers: Certain trustees and/or officers of the Trust are directors and/or officers of BlackRock, Inc. (“BlackRock”) or its affiliates.

It is each Fund’s policy to comply with the requirements of the Internal Revenue Code of 1986, as amended, applicable to regulated investment companies, and to distribute substantially all of its taxable income to its shareholders. Therefore, no U.S. federal income tax provision is required.

Each Fund files U.S. federal and various state and local tax returns. No income tax returns are currently under examination. The statute of limitations on each Fund’s U.S. federal tax returns generally remains open for a period of three years after they are filed. The statutes of limitations on each Fund’s state and local tax returns may remain open for an additional year depending upon the jurisdiction.

Management has analyzed tax laws and regulations and their application to the Funds as of June 30, 2022, inclusive of the open tax return years, and does not believe that there are any uncertain tax positions that require recognition of a tax liability in the Funds’ financial statements.

The number of shares sold, reinvested and redeemed for Institutional were transacted at each class’s floating NAV per share calculated to four decimal places.

Transactions in capital shares for each class of Institutional were as follows: