Form 497K LOOMIS SAYLES FUNDS II

Before you invest, you may want to review the Fund’s Prospectus, which contains more information about the Fund and its risks. You can find the Fund’s Prospectus, reports to shareholders, and other information about the Fund online at www.loomissayles.com/Prospectus. You can also get this information at no cost by calling 800-633-3330 or by sending an e-mail request to [email protected]. The Fund’s Prospectus and Statement of Additional Information (“SAI”), each dated February 1, 2023, as may be revised or supplemented from time to time, are incorporated by reference into this Summary Prospectus.

INVESTMENT OBJECTIVE

The Fund’s investment objective is long-term capital growth from investments in common stocks or other equity securities.

FUND FEES & EXPENSES

The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund.  You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table.

The Fund does not impose a sales charge, a redemption fee or an exchange fee.

Annual Fund Operating Expenses

Example

The example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes for you if your Fund shares are held in a taxable account.

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These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During its most recently ended fiscal year, the Fund’s portfolio turnover rate was 34% of the average value of its portfolio.

INVESTMENTS, RISKS AND PERFORMANCE

Principal Investment Strategies

The Fund normally will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in the equity securities of “small-cap companies,” including preferred stocks, warrants, securities convertible into common or preferred stocks and other equity-like interests in an entity. Currently, the Fund defines a small-cap company to be one whose market capitalization falls within the capitalization range of the Russell 2000^® Index, an index that tracks stocks of 2,000 of the smallest U.S. companies. The Fund may invest the rest of its assets in companies of any size, including large-capitalization companies.

In deciding which securities to buy and sell, Loomis Sayles typically seeks to identify companies that it believes have distinctive products, technologies, or services; dynamic earnings growth; prospects for high levels of profitability; and solid management. Loomis Sayles typically does not consider current income when making buy and sell decisions.

The Fund may invest any portion of its assets in securities of Canadian issuers and up to 20% of its assets in other foreign securities, including emerging markets securities. Although certain equity securities purchased by the Fund may be issued by domestic companies incorporated outside of the United States, the Adviser does not consider these securities to be foreign if they are included in the U.S. equity indices published by S&P Global Ratings or Russell Investments. The Fund may also invest in securities issued pursuant to Rule 1444A under the Securities Act of 1933 (“Rule 144A securities”).

The Fund may engage, for hedging and investment purposes, in foreign currency transactions (such as forward currency contracts), options and futures transactions.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund.

Fund shares are not bank deposits and are not guaranteed, endorsed or insured by the Federal Deposit Insurance Corporation or any other government agency, and are subject to investment risks, including possible loss of the principal invested.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund’s portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

Equity Securities Risk is the risk that the value of a stock may decline for a number of reasons that relate directly to the issuer, such as management performance, financial leverage and reduced demand for the issuer’s goods and services, or the equity markets generally.  Growth stocks are generally more sensitive to market movements than other types of stocks primarily because their stock prices are based heavily on future expectations. If the Adviser’s assessment of the prospects for a company’s growth is wrong, or if the Adviser’s judgment of how other investors will value the company’s growth is wrong, then the price of the company’s stock may fall or not approach the value that the Adviser has placed on it.. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer’s bonds generally take precedence over the claims of those who own preferred stock or common stock.

Small-Capitalization Companies Risk is the risk that the Fund’s investments may be subject to more abrupt price movements, limited markets, increased volatility and less liquidity than investments in larger, more established companies, which could adversely affect the value of the portfolio.

Market/Issuer Risk is the risk that the market value of the Fund’s investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund’s investments, such as management performance, financial condition and demand for the issuers’ goods and services.

Management Risk is the risk that Loomis Sayles’ investment techniques will be unsuccessful and cause the Fund to incur losses.

Credit/Counterparty Risk is the risk that the issuer or guarantor of a fixed-income security in which the Fund invests, or the counterparty to a derivative or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. As a result, the Fund may sustain losses or be unable or delayed in its ability to realize gains.

Currency Risk is the risk that the value of the Fund’s investments will fall as a result of changes in exchange rates. Loomis Sayles may elect not to hedge currency risk or may hedge imperfectly, which may cause the Fund to incur losses that would not have been incurred had the

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risk been hedged.

Cybersecurity and Technology Risk is the risk associated with the increasing dependence of the Fund, its service providers, and other market participants on complex information technology and communications systems. Such systems are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

Derivatives Risk is the risk that the value of the Fund’s derivative investments such as forward currency contracts, options and futures transactions will fall, for example, because of changes in the value of the underlying reference instruments, pricing difficulties or lack of correlation with the underlying investments. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. There is also the risk that the Fund may be unable to terminate or sell a derivative position at an advantageous time or price.  The Fund’s derivative counterparties may experience financial difficulties or otherwise be unwilling or unable to honor their obligations, possibly resulting in losses to the Fund.  This risk is greater for forward currency contracts and other over-the-counter (“OTC”) traded derivatives. Investing in derivatives gives rise to other risks, such as leverage risk, liquidity risk, credit/counterparty risk, interest rate risk and market/issuer risk. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used.

Emerging Markets Risk is the risk that the Fund’s investments in emerging markets may face greater foreign securities risk. Emerging markets investments are subject to greater risks arising from political or economic instability, war, nationalization or confiscatory taxation, currency exchange or repatriation restrictions, sanctions by other countries (such as the United States or the European Union), new or inconsistent government treatment of or restrictions on issuers and instruments, and an issuer’s unwillingness or inability to make dividend, principal or interest payments on its securities. Emerging markets companies may be smaller and have shorter operating histories than companies in developed markets.

Foreign Securities Risk is the risk that the value of the Fund’s foreign investments will fall as a result of foreign political, social, economic, environmental, credit, informational or currency changes or other issues relating to foreign investing generally. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. The Fund’s investments in foreign securities may be subject to foreign withholding or other taxes, which would decrease the yield on those securities.

Large Investor Risk is the risk associated with ownership of shares of the Fund that may be concentrated in one or a few large investors. Such investors may redeem shares in large quantities or on a frequent basis. Redemptions by a large investor can affect the performance of the Fund, may increase realized capital gains, including short-term capital gains taxable as ordinary income, may accelerate the realization of taxable income to shareholders and may increase transaction costs. These transactions potentially limit the use of any capital loss carryforwards and certain other losses to offset future realized capital gains (if any). Such transactions may also increase the Fund’s expenses.

Leverage Risk is the risk associated with securities or investment practices (e.g., borrowing and the use of certain derivatives) that multiply small index, market or asset price movements into larger changes in value. Use of derivative instruments (such as futures and forward currency contracts) may involve leverage. When a derivative is used as a hedge against an offsetting position that the Fund also holds, any gains generated by the derivative should be substantially offset by losses on the hedged instrument, and vice versa. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on the Fund’s returns, and may lead to significant losses if investments are not successful.

Liquidity Risk is the risk that the Fund may be unable to find a buyer for its investments when it seeks to sell them or to receive the price it expects. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund’s investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. During times of market turmoil, there may be no buyers or sellers for securities in certain asset classes. Securities acquired in a private placement, such as Rule 144A securities, are generally subject to significant liquidity risk because they are subject to strict restrictions on resale and there may be no liquid secondary market or ready purchaser for such securities. In other circumstances, liquid investments may become illiquid. Liquidity issues may also make it difficult to value the Fund’s investments. The Fund may invest in liquid investments that become illiquid due to financial distress, or geopolitical events such as sanctions, trading halts or wars.

Risk/Return Bar Chart and Table

The following bar chart and table give an indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual returns for the one-year, five-year, ten-year and life-of-class periods (as applicable) compare to those of a broad measure of market performance. The Fund’s past performance (before and after

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taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at www.loomissayles.com and/or by calling the Fund toll-free at 800-633-3330.

Total Returns for Institutional Class Shares

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for the Institutional Class of the Fund. After-tax returns for the other classes of the Fund will vary. Index performance reflects no deduction for fees, expenses or taxes. The Return After Taxes on Distributions and Sale of Fund Shares for the 1-year period exceeds the Return Before Taxes due to an assumed tax benefit from losses on a sale of Fund shares at the end of the measurement period.

MANAGEMENT

Investment Adviser

Loomis Sayles

Portfolio Managers

Mark F. Burns, CFA^®, Vice President of Loomis Sayles, has served as a portfolio manager of the Fund since 2005.

John J. Slavik, CFA^®, Vice President of Loomis Sayles, has served as a portfolio manager of the Fund since 2005.

PURCHASE AND SALE OF FUND SHARES

The following information shows the investment minimum for various types of accounts:

Retail Class Shares

Retail Class shares of the Fund are subject to a minimum initial investment of $2,500 and a minimum subsequent investment of $50.

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The minimum investment requirements for Retail Class shares of the Fund may be waived or lowered for investments effected through certain financial intermediaries that have entered into special arrangements with Natixis Distribution, LLC (the “Distributor”). Consult your financial intermediary for additional information regarding the minimum investment requirement applicable to your investment.

Institutional Class Shares

Institutional Class shares of the Fund are generally subject to a minimum initial investment of $100,000 and a minimum subsequent investment of $50, except there is no minimum initial or subsequent investment for:

At the discretion of Natixis Advisors, clients of Natixis Advisors, and its affiliates may purchase Institutional Class shares of the Fund below the stated minimums.

Class N Shares

Class N shares of the Fund are subject to a $1,000,000 initial investment minimum. This minimum applies to Fee Based Programs and accounts (such as wrap accounts) where an advisory fee is paid to the broker-dealer or other financial intermediary. There is no subsequent investment minimum for these shares. There is no initial investment minimum for:

In its sole discretion, the Distributor may waive the investment minimum requirement for accounts as to which the Distributor reasonably believes will have enough assets to exceed the investment minimum requirement within a relatively short period of time following the establishment date of such accounts in Class N. The Distributor and the Fund, at any time, reserve the right to liquidate these accounts or any other account that does not meet the eligibility requirements of this class.

Due to operational limitations at your financial intermediary, certain fee based programs, retirement plans, individual retirement accounts and accounts of registered investment advisers may be subject to the investment minimums described above.

The Fund’s shares are available for purchase and are redeemable on any business day through your financial adviser, through your broker-dealer, directly from the Fund by writing to the Fund at Loomis Sayles Funds, P.O. Box 219594, Kansas City, MO 64121-9594, by exchange, by wire, by internet at www.loomissayles.com, by telephone at 800-633-3330, through the Automated Clearing House system, or, in the case of redemptions, by the Systematic Withdrawal Plan. See the section “How Fund Shares are Priced” in the Prospectus for details.

TAX INFORMATION

Fund distributions are generally taxable to you as ordinary income or capital gains, except for distributions to retirement plans and other investors that qualify for tax-advantaged treatment under U.S. federal income tax law generally. Investments in such tax-advantaged plans will generally be taxed only upon withdrawal of monies from the tax-advantaged arrangement.

PAYMENTS TO BROKER-DEALERS AND OTHER FINANCIAL INTERMEDIARIES

If you purchase shares of the Fund through a broker-dealer or other financial intermediary (such as a bank), the Fund and its related companies may pay the intermediary for the sale of the Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your

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salesperson or visit your financial intermediary’s website for more information.

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