UNITED STATES 

SECURITIES AND EXCHANGE COMMISSION 

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER 

PURSUANT TO RULE 13a-16 OR 15d-16 

OF THE SECURITIES EXCHANGE ACT OF 1934

For the month of October 2025

Commission File Number: 001-39240

GFL Environmental Inc. 

(Translation of registrant’s name intoEnglish)

100 New Park Place, Suite 500 

Vaughan, Ontario, Canada L4K 0H9 

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annualreports under cover of Form 20-F or Form 40-F.

Form 20-F ¨              Form 40-F x

Indicateby check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ¨

Indicateby check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ¨

EXHIBIT INDEX

The following Exhibit 99.1 is furnished as part of this CurrentReport on Form 6-K.

SIGNATURE

Pursuant to the requirementsof the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereuntoduly authorized.

Exhibit 99.1

GFL Environmental Inc. Sets Date for Q3 2025 Earnings Release

VAUGHAN, ON, October 8, 2025 – GFL EnvironmentalInc. (NYSE: GFL) (TSX: GFL) (“GFL” or the “Company”) today announced that it will release its 2025 third quarterfinancial results after the market closes on Wednesday November 5, 2025 and will host an investor conference call related to this releaseon Thursday November 6, 2025 at 8:30 am Eastern Time.

A live audio webcastof the conference call can be accessed by logging onto the Company's Investors page at investors.gflenv.com or by clickinghere or listeners may access the call toll-free by dialing 1-833-950-0062 in Canada or 1-833-470-1428 in the United States (accesscode: 255748) approximately 15 minutes prior to the scheduled start time.

TheCompany encourages participants who will be dialing in to pre-register for the conference call using the following link: https://www.netroadshow.com/events/login/LE9zwo3kKYX9JeFFvvHZtzFDghmOmARZi4p.Callers who pre-register will be given a conference access code and PIN to gain immediate access to the call and bypass the live operatoron the day of the call.

About GFL

GFL, headquartered in Vaughan, Ontario, is thefourth largest diversified environmental services company in North America, providing a comprehensive line of solid waste management servicesthrough its platform of facilities throughout Canada and in 18 U.S. states. Across its organization, GFL has a workforce of more than15,000 employees.

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