AFB AllianceBernstein National Municipal Income Fund Inc

ITEM 1. REPORTS TO STOCKHOLDERS.

APR    ^04.30.22

SEMI-ANNUAL REPORT

ALLIANCEBERNSTEIN
NATIONAL MUNICIPAL INCOME FUND
(NYSE: AFB)

As of January 1, 2021, as permitted by new regulations adopted by the Securities and Exchange Commission, the Fund’s annual and semi-annual shareholder reports are no longer sent by mail, unless you specifically requested paper copies of the reports. Instead, the reports are made available on a website, and you will be notified by mail each time a report is posted and provided with a website address to access the report.

You may elect to receive all future reports in paper form free of charge. If you invest through a financial intermediary, you can contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports; if you invest directly with the Fund, you can call Computershare at (800) 219 4218. Your election to receive reports in paper form will apply to all funds held in your account with your financial intermediary or, if you invest directly, to all AB Closed-end Funds you hold.

You may obtain a description of the Fund’s proxy voting policies and procedures, and information regarding how the Fund voted proxies relating to portfolio securities during the most recent 12-month period ended June 30, without charge. Simply visit AB’s website at www.abfunds.com, or go to the Securities and Exchange Commission’s (the “Commission”) website at www.sec.gov, or call AB at (800) 227 4618.

The Fund files its complete schedule of portfolio holdings with the Commission for the first and third quarters of each fiscal year as an exhibit to its reports on Form N-PORT. The Fund’s Form N-PORT reports are available on the Commission’s website at www.sec.gov.

AllianceBernstein Investments, Inc. (ABI) is the distributor of the AB family of mutual funds. ABI is a member of FINRA and is an affiliate of AllianceBernstein L.P., the Adviser of the funds.

The [A/B] logo is a registered service mark of AllianceBernstein and AllianceBernstein^® is a registered service mark used by permission of the owner, AllianceBernstein L.P.

FROM THE PRESIDENT

Dear Shareholder,

We’re pleased to provide this report for the AllianceBernstein National Municipal Income Fund, Inc. (the “Fund”). Please review the discussion of Fund performance, the market conditions during the reporting period and the Fund’s investment strategy.

At AB, we’re striving to help our clients achieve better outcomes by:

Whether you’re an individual investor or a multibillion-dollar institution, we’re putting our knowledge and experience to work for you every day.

For more information about AB’s comprehensive range of products and shareholder resources, please log on to www.abfunds.com.

Thank you for your investment in AB mutual funds—and for placing your trust in our firm.

Sincerely,

Onur Erzan

President and Chief Executive Officer, AB Mutual Funds

SEMI-ANNUAL REPORT

June 7, 2022

This report provides management’s discussion of fund performance for the AllianceBernstein National Municipal Income Fund, Inc. for the semi-annual reporting period ended April 30, 2022. The Fund is a closed-end fund, and its shares are listed and traded on the New York Stock Exchange.

The Fund seeks to provide high current income exempt from regular federal income tax by investing substantially all of its net assets in municipal securities that pay interest that is exempt from federal income tax.

The Fund’s market price per share on April 30, 2022, was $11.63. The Fund’s NAV price per share on April 30, 2022, was $12.98. For additional Financial Highlights, please see pages 47-48.

INVESTMENT RESULTS

The table above shows the Fund’s performance compared to its benchmark, the Bloomberg Municipal Bond Index, for the six- and 12-month periods ended April 30, 2022.

The Fund underperformed the benchmark for both periods. For the six-month period, the Fund’s overweight to municipal credit detracted, relative to the benchmark. Security selection within the prepay-energy sector detracted, while selection in not-for-profit health care contributed.

During the 12-month period, the Fund’s overweight to municipal credit contributed. Security selection in primary/secondary public education detracted, while selection in not-for-profit healthcare contributed.

Leverage, achieved through the usage of tender option bond (“TOB”) and variable rate municipal term preferred shares, contributed to the income of the Fund over both periods, though it detracted from the total return as bond yields rose.

The Fund did not utilize derivatives during the six- or 12-month periods.

MARKET REVIEW AND INVESTMENT STRATEGY

Yields rose toward the end of both the six- and 12-month periods ended April 30, 2022. During the 12-month period, the yield on a 10-Year AAA municipal bond rose to 2.72% from 0.99% and the yield on the 10-Year US Treasury rose to 2.89% from 1.65%. While demand for income remained strong during the first half of the 12-month reporting period, demand weakened during the first quarter of 2022 and into the second quarter, as investors pulled approximately $48 billion from the municipal market as of April 30, 2022.

In addition to broader fixed-income market volatility, these municipal market outflows contributed to municipal underperformance versus US Treasuries, with 10-Year AAA Muni/Treasury after-tax spreads widening 95 basis points (“b.p.”) during the 12-month period and 67 b.p. during the six-month period. Credit spreads were relatively unchanged during the 12-month period, but widened modestly during the six-month period.

The Fund’s Senior Investment Management Team (the “Team”) continues to focus on real after-tax return by investing in municipal bonds that generate income exempt from federal income taxes. The Team relies on an investment process that combines quantitative and fundamental research to build effective bond portfolios.

The Fund may purchase municipal securities that are insured under policies issued by certain insurance companies. Historically, insured municipal securities typically received a higher credit rating, which meant that the issuer of the securities paid a lower interest rate. As a result of declines in the credit quality and associated downgrades of most bond insurers, insurance has less value than it did in the past. The market now values insured municipal securities primarily based on the credit quality of the issuer of the security, with little value given to the insurance feature. In purchasing such insured securities, the Adviser evaluates the risk and return of municipal securities through its own research. If an insurance company’s rating is downgraded or the company becomes insolvent, the prices of municipal securities insured by the insurance company may decline. As of April 30, 2022, the Fund’s percentages of investments in municipal bonds that are insured and in insured municipal bonds that have been pre-refunded or escrowed to maturity were 8.61% and 0.28%, respectively.

INVESTMENT POLICIES

The Fund will normally invest at least 80%, and normally substantially all, of its net assets in municipal securities paying interest that is exempt from regular federal income tax. The Fund also normally will invest at least 75% of its assets in investment-grade municipal securities or

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unrated municipal securities considered to be of comparable quality. The Fund may invest up to 25% of its net assets in municipal bonds rated below investment-grade and unrated municipal bonds considered to be of comparable quality as determined by the Adviser. The Fund intends to invest primarily in municipal securities that pay interest that is not subject to the federal alternative minimum tax (“AMT”), but may invest without limit in municipal securities paying interest that is subject to the federal AMT. For more information regarding the Fund’s risks, please see “Disclosures and Risks” on pages 5-10 and “Note G—Risks Involved in Investing in the Fund” of the Notes to Financial Statements on pages 40-45.

DISCLOSURES AND RISKS

AllianceBernstein National Municipal Income Fund

Shareholder Information

Weekly comparative net asset value (“NAV”) and market price information about the Fund is published each Saturday in Barron’s and in other newspapers in a table called “Closed-End Funds.” Daily NAVs and market price information, and additional information regarding the Fund, is available at www.abfunds.com and www.nyse.com. For additional shareholder information regarding this Fund, please see pages 49-50.

Benchmark Disclosure

The Bloomberg Municipal Bond Index is unmanaged and does not reflect fees and expenses associated with the active management of a mutual fund portfolio. The Bloomberg Municipal Bond Index represents the performance of the long-term tax-exempt bond market consisting of investment-grade bonds. In addition, the Index does not reflect the use of leverage, whereas the Fund utilizes leverage. An investor cannot invest directly in an index, and its results are not indicative of the performance for any specific investment, including the Fund.

A Word About Risk

Among the risks of investing in the Fund are changes in the general level of interest rates or changes in bond credit quality ratings. Changes in interest rates have a greater effect on bonds with longer maturities than on those with shorter maturities. Please note, as interest rates rise, existing bond prices fall and can cause the value of your investment in the Fund to decline. While the Fund invests principally in bonds and other fixed-income securities, in order to achieve its investment objectives, the Fund may at times use certain types of investment derivatives, such as options, futures, forwards and swaps. These instruments involve risks different from, and in certain cases, greater than, the risks presented by more traditional investments. At the discretion of the Fund’s Adviser, the Fund may invest up to 25% of its net assets in municipal bonds that are rated below investment-grade (i.e., “junk bonds”). These securities involve greater volatility and risk than higher-quality fixed-income securities.

Financing and Related Transactions; Leverage and Other Risks: The Fund utilizes leverage to seek to enhance the yield and NAV attributable to its common stock. These objectives may not be achieved in all interest-rate environments. Leverage creates certain risks for holders of common stock, including the likelihood of greater volatility of the NAV and market price of the common stock. If income from the securities purchased from the funds made available by leverage is not sufficient to cover the cost of leverage, the Fund’s return will be less than if leverage had not been used.

As a result, the amounts available for distribution to common stockholders as dividends and other distributions will be reduced. During periods of rising

DISCLOSURES AND RISKS (continued)

short-term interest rates, the interest paid on the preferred shares or floaters in TOB transactions would increase, which may adversely affect the Fund’s income and distribution to common stockholders. A decline in distributions would adversely affect the Fund’s yield and possibly the market value of its shares. If rising short-term rates coincide with a period of rising long-term rates, the value of the long-term municipal bonds purchased with the proceeds of leverage would decline, adversely affecting the NAV attributable to the Fund’s common stock and possibly the market value of the shares.

The Fund’s outstanding Variable Rate MuniFund Term Preferred Shares result in leverage. The Fund may also use other types of financial leverage, including TOB transactions, either in combination with, or in lieu of, the preferred shares. In a TOB transaction, the Fund may transfer a highly rated fixed-rate municipal security into a special purpose entity (typically, a trust). The Fund receives cash and a residual interest security (sometimes referred to as an “inverse floater”) issued by the trust in return. The trust simultaneously issues securities, which pay an interest rate that is reset each week based on an index of high-grade short-term [seven-day] demand notes. These securities, sometimes referred to as “floaters”, are bought by third parties, including tax-exempt money market funds, and can be tendered by these holders to a liquidity provider at par, unless certain events occur. The Fund continues to earn all the interest from the transferred bond less the amount of interest paid on the floaters and the expenses of the trust, which include payments to the trustee and the liquidity provider and organizational costs. The Fund also uses the cash received from the transaction for investment purposes or to retire other forms of leverage. Under certain circumstances, the trust may be terminated and collapsed, either by the Fund or upon the occurrence of certain events, such as a downgrade in the credit quality of the underlying bond, or in the event holders of the floaters tender their securities to the liquidity provider. See Note H to the financial statements for more information about TOB transactions.

The use of derivative instruments by the Fund, such as forwards, futures, options and swaps, may also result in a form of leverage.

Because the advisory fees received by the Adviser are based on the total net assets of the Fund (including assets supported by the proceeds of the Fund’s outstanding preferred shares), the Adviser has a financial incentive for the Fund to keep its preferred shares outstanding, which may create a conflict of interest between the Adviser and the common shareholders of the Fund.

Tax Risk: There is no guarantee that the income on the Fund’s municipal securities will be exempt from regular federal income and state income

DISCLOSURES AND RISKS (continued)

taxes. Unfavorable legislation, adverse interpretations by federal or state authorities, litigation or noncompliant conduct by the issuer of a municipal security could affect the tax-exempt status of municipal securities. If the Internal Revenue Service or a state authority determines that an issuer of a municipal security has not complied with applicable requirements, interest from the security could become subject to regular federal income tax and/or state personal income tax, possibly retroactively to the date the security was issued, the value of the security could decline significantly, and a portion of the distributions to Fund shareholders could be recharacterized as taxable. Recent federal legislation included reductions in tax rates for individuals, with relatively larger reductions in tax rates for corporations. These tax rate reductions may reduce the demand for municipal bonds which could reduce the value of municipal bonds held by the Fund.

Market Risk: The market value of a security may move up or down, sometimes rapidly and unpredictably. These fluctuations may cause a security to be worth less than the price originally paid for it, or less than it was worth at an earlier time. Market risk may affect a single issuer, industry, sector of the economy or the market as a whole. Global economies and financial markets are increasingly interconnected, which increases the probabilities that conditions in one country or region might adversely impact issuers in a different country or region. Conditions affecting the general economy, including political, social, or economic instability at the local, regional, or global level may also affect the market value of a security. Health crises, such as pandemic and epidemic diseases, as well as other incidents that interrupt the expected course of events, such as natural disasters, including fires, earthquakes and flooding, war or civil disturbance, acts of terrorism, power outages and other unforeseeable and external events, and the public response to or fear of such diseases or events, have had, and may in the future have, an adverse effect on the Fund’s investments and NAV and can lead to increased market volatility. For example, the diseases or events themselves or any preventative or protective actions that governments may take in respect of such diseases or events may result in periods of business disruption, inability to obtain raw materials, supplies and component parts, and reduced or disrupted operations for issuers of securities held by the Fund. The occurrence and pendency of such diseases or events could adversely affect the economies and financial markets either in specific countries or worldwide.

Municipal Market Risk: This is the risk that special factors may adversely affect the value of the municipal securities and have a significant effect on the yield or value of the Fund’s investments in municipal securities. These factors include economic conditions, political or legislative changes, public health crises, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. To the extent that the Fund

DISCLOSURES AND RISKS (continued)

invests more of its assets in a particular state’s municipal securities, the Fund may be vulnerable to events adversely affecting that state, including economic, political and regulatory occurrences, court decisions, terrorism, public health crises (including the occurrence of a contagious disease or illness) and catastrophic natural disasters, such as hurricanes, fires or earthquakes. For example, the novel coronavirus (COVID-19) pandemic has significantly stressed the financial resources of many issuers of municipal securities, which could impair any such issuer’s ability to meet its financial obligations when due and adversely impact the value of its securities held by the Fund. As the full effects of the COVID-19 pandemic on state and local economies and on issuers of municipal securities are still uncertain, the financial difficulties of issuers of municipal securities may continue or worsen, adversely affecting the performance of the Fund. The Fund’s investment in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project’s ability to make payments of principal and interest on these securities.

Credit Risk: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations.

Interest-Rate Risk: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest-rate risk is generally greater for fixed-income securities with longer maturities or durations. The current historically low interest rate environment heightens the risks associated with rising interest rates.

Inflation Risk: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Fund’s assets can decline as can the value of the Fund’s distributions. This risk is significantly greater for fixed-income securities with longer maturities.

DISCLOSURES AND RISKS (continued)

Derivatives Risk: The Fund may enter into derivative transactions such as forwards, options, futures and swaps. Derivatives may be difficult to price or unwind and leveraged so that small changes may produce disproportionate losses for the Fund. Derivatives, especially over-the-counter derivatives, are also subject to counterparty risk, which is the risk that the counterparty (the party on the other side of the transaction) on a derivative transaction will be unable or unwilling to honor its contractual obligations to the Fund. Derivatives may result in significant losses, including losses that are far greater than the value of the derivatives reflected on the statement of assets and liabilities.

Illiquid Investments Risk: Illiquid investments risk exists when particular investments are or become difficult to purchase or sell, possibly preventing the Fund from selling out of these securities at an advantageous price. Causes of illiquid investments risk may include low trading volumes, large positions and heavy redemptions of Fund shares. Illiquid investments risk may be magnified in a rising interest-rate environment, when the value and liquidity of fixed-income securities generally decline. Derivatives and securities involving substantial market and credit risk tend to involve greater illiquid investments risk than most other types of investments. The Fund is subject to illiquid investments risk because the market for municipal securities is generally smaller than many other markets, which may make municipal securities more difficult to trade than other types of securities. Illiquid securities may also be difficult to value.

Duration Risk: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

Management Risk: The Fund is subject to management risk because it is an actively managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, but there is no guarantee that its techniques will produce the intended results. Some of these techniques may incorporate, or rely upon, quantitative models, but there is no guarantee that these models will generate accurate forecasts, reduce risk or otherwise perform as expected.

These risks are fully discussed in the Fund’s prospectus. As with all investments, you may lose money by investing in the Fund.

An Important Note About Historical Performance

The performance shown in this report represents past performance and does not guarantee future results. Current performance may be lower or higher than the performance information shown. All fees

DISCLOSURES AND RISKS (continued)

and expenses related to the operation of the Fund have been deducted. Performance assumes reinvestment of distributions and does not account for taxes. Historical performance does not reflect the deduction of taxes that a shareholder would pay on fund distributions or the sale of fund shares and assumes the reinvestment of dividends and capital gains distributions at prices obtained pursuant to the Fund’s dividend reinvestment plan.

Performance assumes the reinvestment of dividends and capital gains distributions at prices obtained pursuant to the Fund’s dividend reinvestment plan.

PORTFOLIO SUMMARY

April 30, 2022 (unaudited)

PORTFOLIO STATISTICS

Net Assets ($mil): $373.2

As of April 30, 2022, the Fund’s percentages of investments in municipal bonds that are insured and in insured municipal bonds that have been pre-refunded or escrowed to maturity are 8.6% and 0.3%, respectively.

PORTFOLIO OF INVESTMENTS (continued)

Glossary:

AGC – Assured Guaranty Corporation

AGM – Assured Guaranty Municipal

BAM – Build American Mutual

ETM – Escrowed to Maturity

OSF – Order of St. Francis

See notes to financial statements.