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Date of Report (Date of earliest event reported): May 19, 2026

(Exact name of registrant as specified in its charter)

(Registrant’s telephone number,
including area code)

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligations of the registrant under any of the following provisions:

o    Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o    Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o    Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o    Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240-13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b–2 of the Securities Exchange Act of 1934 (§240.12b–2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

The 2026 Annual Meeting of Stockholders (the “Annual Meeting”) of Hyliion Holdings Corp. (“Hyliion” or the “Company”) was held on May 19, 2026. At the Annual Meeting:

•Stockholders elected the three nominees recommended by the Company’s board of directors to serve as Class III directors of the Company until the 2029 Annual Meeting of Stockholders or until their respective successors are elected and qualified;

•Stockholders ratified the selection of Grant Thornton LLP (the “Auditor”) to serve as the independent registered public accounting firm of the Company for the 2026 fiscal year ended December 31, 2026;

•Stockholders approved, on an advisory basis, the compensation of the Company’s named executive officers (“Say on Pay”); and

•Stockholders approved an amendment to the Hyliion Holdings Corp. 2024 Equity Incentive Plan.

Set forth below, with respect to each such matter, are the number of votes cast for or against/withhold, the number of abstentions and the number of broker non-votes.

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