William Kreutzmann Jr. (/ˈkrɔɪtsmɑːn/ KROYTS-mahn; born May 7, 1946) is an American drummer and founding member of the Grateful Dead rock band. He played with the Grateful Dead 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 started playing drums at the age of 13. At first he practiced on a Slingerland drum kit lent to him. As a teenager, he was practicing drums alone in a large building at his high school when Aldous Huxley and another man walked in. Huxley told Bill he’d never heard anything like it, and encouraged him in his drumming – despite the fact Bill had been told by his sixth grade music teacher that he could not keep a beat. Kreutzmann continued to practice a great deal. His earliest enthusiasm was for the music of Ray Charles and other R&B musicians. He has explained that later he learned some advanced technique or tricks from Mickey Hart.