William Kreutzmann Jr. (/ˈkrɔɪtsmɑːn/ KROYTS-mahn; born May 7, 1946) is an American drummer. 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 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.

Kreutzmann started playing drums at the age of 13. At first he practiced on a Slingerland drum kit lent to him. As a teenager, practicing drums alone in a large building at his high school, 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.

Kreutzmann listened to jazz groups in clubs when he found an opportunity for an under-age guy to get in. After joining the Warlocks (later called the Grateful Dead), bassist Phil Lesh introduced him the work of one of the top jazz drummers of the time, Elvin Jones. Kreutzmann became an enthusiast, also, for the funk music of The Meters.