Prospectus by Investment Company (Form 497)

Supplement dated September 24, 2026 to the Funds' Statement of Additional Information ("SAI"), dated May 1, 2026 as may be revised or supplemented from time to time.

NATIXIS OAKMARK fund

NATIXIS U.S. EQUITY OPPORTUNITIES FUND

(each, a "Fund," together, the "Funds")

Effectively immediately, the Expense Limitations table and lead-in information within the section "Advisory Fees - Fund Charges and Expenses" of the SAI are hereby amended and replaced as follows, with respect to the Funds:

Natixis Advisors, in the case of Natixis Oakmark Fund, Natixis Oakmark International Fund and U.S. Equity Opportunities Fund, and Loomis Sayles, in the case of High Income Fund, International Growth Fund, Investment Grade Bond Fund, Strategic Alpha Fund and Strategic Income Fund, have each given a binding contractual undertaking for all classes of the Funds in the table below to waive the advisory fees and, if necessary, to reimburse certain expenses related to operating the Funds in order to limit the Funds' expenses, exclusive of acquired fund fees and expenses, brokerage expenses, interest expense, taxes and organizational and extraordinary expenses, such as litigation and indemnification expenses, to the annual rates indicated below. The undertakings are in effect through April 30, 2027, and will be reevaluated on an annual basis and may be terminated before then only with the consent of the Funds' Board. Natixis Advisors and Loomis Sayles will be permitted to recover, on a class-by-class basis, expenses it has borne through the undertaking described above (whether through waiver of its advisory fee or otherwise) to the extent that a class's expenses in later periods fall below the annual rate set forth in the relevant undertaking. The Funds will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fee/expense was waived/reimbursed.