Mentzer is a surname. Notable people with the surname include:
Ethan Mentzer, member of the Click Five
Frank Mentzer, American fantasy author
John Thomas Mentzer, University of Tennessee marketing and logistics professor
Mike Mentzer, American IFBB professional bodybuilder
Ray Mentzer, bodybuilder and brother of Mike Mentzer
Steven Mentzer, Republican member of the Pennsylvania House of Representatives
Susanne Mentzer, operatic mezzo-soprano
William C. Mentzer, aeronautical engineer