William Henry Marcus Miller Jr. (born June 14, 1959) is an American film composer, jazz composer, record producer, arranger, and multi-instrumentalist, best known as a bassist. He has worked with trumpeter Miles Davis, pianist Herbie Hancock, singer Luther Vandross, and saxophonist David Sanborn, among others.

Miller was born in Brooklyn, New York City, in 1959 and raised in a musical family. His father, William Miller, was a church organist and choir director; Miller is jazz pianist Wynton Kelly‘s cousin. Miller is classically trained as a clarinetist and also plays keyboards, saxophone and guitar. He began to work regularly in New York City, eventually playing bass and writing music for jazz flutist Bobbi Humphrey and keyboardist Lonnie Liston Smith. Miller became a session musician.