Natixis Funds Trust I


	Summary Prospectus December 28, 2018, as revised February 12, 2019

Mirova International Sustainable Equity Fund

Ticker Symbol: Class A (MRVAX), Class N (MRVNX) and Class Y (MRVYX)

Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the reports from the Fund or from your financial intermediary, such as a broker-dealer or bank. Instead, the reports will be made available on the Funds’ website, and you will be notified by mail each time a report is posted and provided with a website link to access the report. If you wish to continue receiving paper copies of your shareholder reports after January 1, 2021, you can inform the Fund at any time by calling 1-800-225-5478. If you hold your account with a financial intermediary and you wish to continue receiving paper copies after January 1, 2021, you should call your financial intermediary directly. Paper copies are provided free of charge, and your election to receive reports in paper will apply to all funds held with the Natixis Funds complex. If you have already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. You currently may elect to receive shareholder reports and other communications from the Fund or your financial intermediary electronically at www.icsdelivery.com/natixisfunds.

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 im.natixis.com/fund-documents. You can also get this information at no cost by calling 800-225-5478 or by sending an e-mail request to NatixisFunds@natixis.com. The Fund’s Prospectus and Statement of Additional Information, each dated December 28, 2018, as may be revised or supplemented from time to time, are incorporated by reference into this Summary Prospectus.

Investment Goal

The Fund seeks long-term capital appreciation.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section “How Sales Charges Are Calculated” on page 10 of the Prospectus, in Appendix A to the Prospectus and on page 75 in the section “Reduced Sales Charges” of the Statement of Additional Information (“SAI”).

Shareholder Fees


(fees paid directly from your investment)	Class A	Class N	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%	None	None
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	None*	None	None
Redemption fees	None	None	None

*	A 1.00% contingent deferred sales charge (“CDSC”) may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

Annual Fund Operating Expenses


(expenses that you pay each year as a percentage of the value of your investment)	Class A	Class N	Class Y
Management fees	0.80%	0.80%	0.80%
Distribution and/or service (12b-1) fees	0.25%	0.00%	0.00%
Other expenses¹	0.94%	0.84%	0.94%
Total annual fund operating expenses	1.99%	1.64%	1.74%
Fee waiver and/or expense reimbursement²	0.79%	0.74%	0.79%
Total annual fund operating expenses after fee waiver and/or expense reimbursement	1.20%	0.90%	0.95%

1	Other expenses are estimated for the current fiscal year.

Ostrum Asset Management U.S., LLC (“Ostrum US” or the “Adviser”) has given a binding contractual undertaking to the Fund to limit the amount of the Fund’s total annual fund operating expenses to 1.20%, 0.90% and 0.95% of the Fund’s average daily net assets for Class A, N and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2020 and may be terminated before then only with the consent of the Fund’s Board of Trustees. The Adviser will be permitted to recover, on a class-by-class

Fund Summary

basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below the applicable expense limitation for Class A, N and Y shares. The Fund 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 fees or expenses were waived/reimbursed.

Example

This 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 (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same, except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement assuming that such waiver and/or reimbursement will only be in place through the date noted above and on the Total Annual Fund Operating Expenses for the remaining periods. Although your actual costs may be higher or lower, based on these assumptions your costs would be:


	1 year		3 years
Class A	$	690	$	1,065
Class N	$	92	$	419
Class Y	$	97	$	443

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. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

Investments, Risks and Performance

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its assets in equity securities, which may include common stocks, preferred stocks, depositary receipts and real estate investment trusts (“REITS”). The Fund invests in securities of companies located in no fewer than three countries outside the U.S. Under normal circumstances, the Fund will invest at least 65% of its assets in securities of companies located outside the U.S. and the Fund may invest up to 25% of its assets in securities of companies located in emerging markets (which generally encompasses markets that are not included in the MSCI World Developed Markets Index). The Fund may invest in growth and value companies of any size and may also invest in initial public offerings (“IPOs”).

The Adviser applies a thematic approach to investment idea generation, investing in securities of companies that it believes offer solutions to the major transitions that our world is going through. These transitions include (i) demographics, such as an aging population, (ii) environmental issues, such as water scarcity, (iii) technological advances, such as cloud computing, and (iv) governance changes, such as the growing importance of corporate responsibility. From this large universe of solution providers, the Adviser applies detailed fundamental research to select companies that it believes are well managed, are expected to benefit from strong, sustainable competitive advantages, and have demonstrated a solid financial structure while avoiding irresponsible risks. The Adviser seeks to invest in securities that are trading at significant discounts to what the Adviser believes are their intrinsic values. Furthermore, the Adviser seeks to invest in companies with a positive impact on the United Nations’ Sustainable Development Goals (the “SDGs”), while avoiding companies whose activities or products have a negative impact on or create a risk to achieving the SDGs. The Adviser believes that this approach will result in a portfolio with a better environmental and social profile than the broad equities market.

The Adviser may sell a security due a deterioration in the company’s fundamental quality, a change in thematic exposure or impact relative to the SDGs, a controversy alert such as one relating to human rights, or if the Adviser believes the security has little potential for price appreciation or there is greater relative value in other securities in the Fund’s investment universe.

Principal Investment 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.

Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund will be subject to currency risk because it will invest in securities or other instruments denominated in, or that generate income denominated in, foreign currencies. The Fund will not hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer’s unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in developed markets.

Equity Securities Risk: The value of the Fund’s investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. Securities issued in IPOs tend to involve

Fund Summary

greater market risk than other equity securities due, in part, to public perception and the lack of publicly available information and trading history. 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. Value stocks can perform differently from the market as a whole and from other types of stocks. Value stocks also present the risk that their lower valuations fairly reflect their business prospects and that investors will not agree that the stocks represent favorable investment opportunities, and they may fall out of favor with investors and underperform growth stocks during any given period. 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. Securities of real estate-related companies and REITs in which the Fund may invest may be considered equity securities, thus subjecting the Fund to the risks of investing in equity securities generally.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund’s investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Large Investor Risk: Ownership of shares of the Fund 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.

Management Risk: A strategy used by the Fund’s portfolio managers may fail to produce the intended result.

Market/Issuer Risk: 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.

REITs Risk: Investments in the real estate industry, including REITs, are particularly sensitive to economic downturns and are sensitive to factors such as changes in real estate values, property taxes and tax laws, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents and the management skill and creditworthiness of the issuer. Companies in the real estate industry also may be subject to liabilities under environmental and hazardous waste laws. In addition, the value of a REIT is affected by changes in the value of the properties owned by the REIT or mortgage loans held by the REIT. REITs are also subject to default and prepayment risk. Many REITs are highly leveraged, increasing their risk. The Fund will indirectly bear its proportionate share of expenses, including management fees, paid by each REIT in which it invests in addition to the expenses of the Fund.

Small- and Mid-Capitalization Companies Risk: Compared to large-capitalization companies, small- and mid-capitalization companies are more likely to have limited product lines, markets or financial resources. Stocks of these companies often trade less frequently and in limited volume and their prices may fluctuate more than stocks of large-capitalization companies. As a result, it may be relatively more difficult for the Fund to buy and sell securities of small- and mid-capitalization companies.

Sustainable Investment Style Risk: Because the Fund focuses on investments in companies that relate to certain sustainable development themes and demonstrate adherence to environmental, social and governance (“ESG”) practices, its universe of investments may be smaller than that of other funds and therefore the Fund may underperform the market as a whole if such investments underperform the market. The Fund may forgo opportunities to gain exposure to certain companies, industries, sectors or countries and it may choose to sell a security when it might otherwise be disadvantageous to do so.

Risk/Return Bar Chart and Table

Because the Fund has not yet completed a full calendar year, information related to Fund performance, including a bar chart showing annual returns, has not been included in this Prospectus. The performance information provided by the Fund in the future will give some indication of the risks of an investment 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 compare against those of a broad measure of market performance. The Fund’s past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

Management

Investment Adviser

Ostrum Asset Management U.S., LLC (“Ostrum US” formerly, Natixis Asset Management U.S., LLC)

Portfolio Managers

Jens Peers, CFA^®, has served as co-portfolio manager of the Fund since 2018.

Hua Cheng, CFA^®, PhD, has served as co-portfolio manager of the Fund since 2018.

Amber Fairbanks, CFA^®, has served as a co-portfolio manager of the Fund since 2018.

Fund Summary

Purchase and Sale of Fund Shares

Class A Shares

The following chart shows the investment minimums for various types of accounts:


Type of Account	Minimum Initial Purchase		Minimum Subsequent Purchase
Any account other than those listed below	$	2,500	$	50
For shareholders participating in Natixis Funds’ Investment Builder Program	$	1,000	$	50
For Traditional IRA, Roth IRA, Rollover IRA, SEP-IRA and Keogh plans using the Natixis Funds’ prototype document (direct accounts, not held through intermediary)	$	1,000	$	50
Coverdell Education Savings Accounts using the Natixis Funds’ prototype document (direct accounts, not held through intermediary)	$	500	$	50

There is no initial or subsequent investment minimum for:

Class N Shares

Class N shares of the Fund are subject to a $1,000,000 initial investment minimum. There is no initial investment minimum for Certain Retirement Plans and funds of funds that are distributed by Natixis Distribution, L.P. (the “Distributor”). Sub-accounts held within an omnibus account, where the omnibus account has at least $1,000,000, are not required to meet the investment minimum. There is no subsequent investment minimum for these shares. 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. If, after two years, an account’s value does not exceed the investment minimum requirement, the Distributor and the Fund reserve the right to redeem such account.

Class Y Shares

Class Y 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:

• Wrap Fee Programs of certain broker-dealers, the advisers or Natixis Distribution, L.P. Please consult your financial representative to determine if your wrap fee program is subject to additional or different conditions or fees.
• Certain Retirement Plans. Please consult your retirement plan administrator to determine if your retirement plan is subject to additional or different conditions or fees.
• Certain Individual Retirement Accounts if the amounts invested represent rollover distributions from investments by any of the retirement plans invested in the Fund.
• Clients of a Registered Investment Adviser where the Registered Investment Adviser receives an advisory, management or consulting fee.
• Fund Trustees, former Fund trustees, employees of affiliates of the Natixis Funds and other individuals who are affiliated with any Natixis Fund (this also applies to any spouse, parents, children, siblings, grandparents, grandchildren and in-laws of those mentioned) and Natixis affiliate employee benefit plans.

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

Due to operational limitations at your financial intermediary, certain wrap fee 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 investment dealer, directly from the Fund by writing to the Fund at Natixis Funds, P.O. Box 219579, Kansas City, MO 64121-9579, by exchange, by wire, by internet at im.natixis.com (certain restrictions may apply), through the Automated Clearing House system, or, in the case of redemptions, by telephone at 800-225-5478 or by the Systematic Withdrawal Plan.

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


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