Joseph L. Greenstein (January 2, 1893 – October 8, 1977), better known as The Mighty Atom, was a 20th-century strongman known for highly unusual feats of strength and endurance.

Greenstein traveled with Volanko and the Issakoff Brothers Circus for eighteen months, learning the strongman's training regimen.

[2] This experience sparked Greenstein's interest in the mental powers associated with strength, and he gradually developed an array of strongman feats.

He traveled in an old Model A truck with panels that opened to show his extensive collection of newsclippings and citations from civic leaders and organizations.

[8] Joe's 93-year-old son Mike Greenstein appeared on America's Got Talent in 2014 and successfully pulled a 3,500-pound (1,600 kg) car with his teeth.