Siegmund Klein (April 10, 1902 – May 24, 1987) was a German-American strongman, bodybuilder, magazine publisher, and gymnasium owner prominent in physical culture.

A reader of strength magazines, and admirer of his father's muscular arms, Klein began his own weight training at age 12 with an improvised use of window counterweights.

[3] In 1924, Klein arrived in New York City and arranged to take over operation of a gymnasium previously owned by Louis Attila, the inventor of the bent press weight training exercise and trainer of pioneering bodybuilder Eugen Sandow.

[11] The organization that became the Association of Oldtime Barbell and Strongmen (AOBS) began with Vic Boff, Leo Murdock, and others putting together a surprise 80th birthday party for Klein in 1982.

The strong interest by attendees at this and several followup events solidified the formation of a group that honors old time champions and preserves weightlifting history.