William Kreutzmann Jr. (/ˈkrɔɪtsmɑːn/ KROYTS-mahn; born May 7, 1946) is an American drummer and founding member of the rock band Grateful Dead. He played with the band for its entire thirty-year career, usually alongside fellow drummer Mickey Hart, and has continued to perform with former members of the Grateful Dead in various lineups, and with his own bands BK3, 7 Walkers and Billy & the Kids.

Kreutzmann was born in Palo Alto, California, the son of Janice Beryl (née Shaughnessy) and William Kreutzmann Sr. His father was of German descent. His maternal grandfather was football coach and innovator Clark Shaughnessy.