William Parker (born January 10, 1952) is an American free jazz double bassist. Beginning in the 1980s, Parker played with Cecil Taylor for over a decade, and he has led the Little Huey Creative Music Orchestra since 1981. The Village Voice named him “the most consistently brilliant free jazz bassist of all time” and DownBeat has called him “one of the most adventurous and prolific bandleaders in jazz”.

Parker was born in the Bronx, New York City, and grew up in the Melrose housing project. His first instrument was the trumpet, followed by the trombone and cello. Parker was not formally trained as a classical player, but in his youth studied with Jimmy Garrison, Richard Davis, and Wilbur Ware in learning the tradition.

While Parker has been active since the early 1970s, he first came to public attention playing with pianist Cecil Taylor in the 1980s. He has performed in many of Peter Brötzmann‘s groups, and played with saxophonist David S. Ware from 1989 until his last concert performance in 2011. He is a member of the Other Dimensions In Music cooperative. His work as leader came to greater prominence in the 1990s with groups such as the Little Huey Creative Music Orchestra and In Order to Survive.