Exhibit 31.1

Certification of Principal Executive Officer

I, Brian A. Kenney, certify that:

1. I have reviewed this Amendment No. 1 to the Annual Report on Form 10-K of GATX Corporation (the "Company"); and

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report.

/s/    BRIAN A. KENNEY        

Brian A. Kenney

Chairman, President and Chief Executive Officer

March 30, 2021