Charles Anthony "Buster" Williams Jr. was born April 17, 1942, in Camden, New Jersey. His father, Charles Anthony Williams Sr., played bass, drums, and piano and held band rehearsals in the family home, so the son grew up inside the music. What settled the instrument for him was his father's record of "Star Dust" featuring Oscar Pettiford. He was still in junior high school when he took his first professional job, covering a date his father had double-booked. As a teenager he practiced with the pianist Sam Dockery, who was working in Jimmy Heath's Philadelphia band on a regular double bill with the alto saxophonist Sam Reed. When his father handed him a Monday night of his own at a club called Rip's in 1959, Williams hired Reed for the gig, calculating that it would put him in front of Heath. Two days later Reed called him for work, and Heath hired him the week after that. Williams graduated from Camden High School in 1960 and later studied composition, harmony, and theory with Dr. Roland Wiggins at Combs College of Music in Philadelphia, attending irregularly around his touring schedule.

The Rip's strategy set a pattern. In 1960 the bassist Nelson Boyd called Williams Sr. to cover a Philadelphia weekend with Gene Ammons and Sonny Stitt, and the father again sent his son. After the first set on the Friday night, Ammons and Stitt asked the eighteen-year-old to come on tour. He stayed roughly a year, from 1960 into 1961, until the band was stranded in Kansas City and the rhythm section had to take a week's work with Al Hibbler to buy train fare home. His first two recordings came out of that association, both cut in Chicago in August 1961: Dig Him! for Argo and Boss Tenors for Verve. Singers came next, and they defined the rest of the decade. Dakota Staton hired him in 1961 after hearing him in Wilmington, Delaware; Betty Carter followed in 1962 and Sarah Vaughan in 1963, taking him on his first European tour. From 1964 he worked steadily with Nancy Wilson, recording several Capitol albums with her and moving to Los Angeles to be near the work.

The West Coast years widened his range fast. Alongside Wilson he recorded five Pacific Jazz albums with the Jazz Crusaders, worked with Kenny Dorham, and cut a date with the Harold Land and Bobby Hutcherson quintet. By his own account he was the first call whenever Ray Brown was unavailable. In 1967 he spent several months in the Miles Davis Quintet, substituting for Ron Carter, and it was there that he met Herbie Hancock. Little of that tenure was recorded: his only trace in the Davis catalog is a single 1967 Hollywood session added as a bonus track to the CD reissue of Sorcerer, an album whose original LP has Carter on every track.

Williams moved to New York in October 1968 and became one of the busiest bassists in the city. He played with Art Blakey, Herbie Mann, and Mary Lou Williams, and recorded for Atlantic, Blue Note, and Prestige behind McCoy Tyner, Dexter Gordon, Roy Ayers, Stanley Turrentine, Frank Foster, Illinois Jacquet, and Ammons again, the last newly out of a seven-year sentence at Joliet. The connection made in the Davis quintet then paid off: Hancock brought him into the band that became the Mwandishi Sextet, and Williams held the bass chair for its entire run. He is on The Prisoner (recorded at Van Gelder Studio in April 1969) and Fat Albert Rotunda (1969), then on the three albums that define the group, Mwandishi (Warner Bros., 1971), Crossings (Warner Bros., 1972), and Sextant (Columbia, 1973), and on two Capricorn dates under Eddie Henderson's name. The sextet ran acoustic bass, electric bass, Fender Rhodes, Moog, and ARP synthesizers through a band that also held Bennie Maupin, Julian Priester, Henderson, and Billy Hart, and every member took a Swahili name. Williams became Mchezaji, a credit that still appears on the sleeve of Mwandishi beside his own.

His first album as a leader, Pinnacle, was recorded at Blue Rock Studios in New York across four August days in 1975 and released on Muse, with Hart on drums, Sonny Fortune on saxophones and flute, Woody Shaw on trumpet, Earl Turbinton on reeds, and Onaje Allan Gumbs on keyboards. Four more leader dates followed by 1980: Crystal Reflections (Muse, 1976), the trio record Tokudo with Kenny Barron and Ben Riley (Denon, cut in Tokyo in January 1978), Heartbeat (Muse, recorded in 1978), and the string-augmented Dreams Come True (Buddah, recorded in 1978 and issued in 1980). He also anchored the three Milestone albums on which Ron Carter soloed on piccolo bass, and he was nominated for a Grammy Award for Love for Sale, the first record credited to The Great Jazz Trio, with Hank Jones and Tony Williams. Then his own recording almost stopped: between 1980 and 1998 he made just one album under his own name, Something More (In+Out, 1989), cut over two days in March at Van Gelder Studio with Hancock, Wayne Shorter, Al Foster, and trumpeter Shunzo Ohno, and carrying five Williams originals. Something More became the name of his working band from 1990 onward.

The gap in leader dates was not a gap in work. In 1982 Williams joined two collective bands at once. The Timeless All Stars put him with Harold Land, Curtis Fuller, Hutcherson, Cedar Walton, and Billy Higgins; their first album, It's Timeless, was taped live at Keystone Korner in San Francisco on April 28, 1982. Sphere, with Barron, Riley, and Charlie Rouse, began as a Thelonious Monk tribute and made its first record for Elektra/Musician on February 17, 1982, the day Monk died, before broadening into standards and the members' own writing. Sphere ran until Rouse's death in 1988 and reconvened from 1997 to 2002 with Gary Bartz in the saxophone chair. Across the same decades Williams toured with Hancock, recorded with Larry Coryell, Stanley Cowell, Steve Turre, Frank Morgan, Chet Baker, Emily Remler, and Shirley Horn, and did steady studio work for film and television, including Mackenna's Gold under Quincy Jones in 1969, Angelo Badalamenti's score for Twin Peaks: Fire Walk with Me, and Terence Blanchard's for Clockers.

From 1997 the leader records resumed and kept coming: Somewhere Along the Way, Lost in a Memory, Live at the Montreux Jazz Festival 1999, and Joined at the Hip for the Swiss label TCB, Houdini for Sirocco (recorded in Brooklyn in March 2000 with Geri Allen and Lenny White), and Griot Libertè for HighNote, recorded at Van Gelder Studio in February 2004, engineered and mastered by Rudy Van Gelder, and issued as a hybrid SACD with a five-channel surround mix. 65 Roses came from a 2006 cystic fibrosis benefit concert in Mountain View, California, with Barron and White; Live Volume 1 was self-released as a download in 2008. Two Smoke Sessions albums followed, Audacity in 2018 and Unalome in 2023, the latter credited to the Buster Williams Something More Septet. He has also worked in a string of long-running groups: 4 Generations of Miles with Fortune, Mike Stern, and Jimmy Cobb; a trio with Cyrus Chestnut and White; the Wallace Roney Quintet; and Denny Zeitlin's trio with Matt Wilson.

Williams and his wife Veronica, whom he met in junior high school and married in 1965, took up the Nichiren Buddhist practice of chanting Nam-myoho-renge-kyo in 1972 after she was concussed in a car accident, and he has remained a member of Soka Gakkai International since. Griot Libertè was written out of a later health crisis, Veronica's recovery from a coma following a heart attack. He founded the Buster Williams School of Music as a non-profit in 2013, growing it out of a summer class he had run the previous year for the IDEA Performing Arts Center in Camden. Adam Kahan's documentary Buster Williams: Bass to Infinity was released in 2019. In February 2026 the Mellon Foundation and the Jazz Foundation of America named him to the second cohort of Jazz Legacies Fellows, an award of $100,000 in unrestricted funds plus stipends, and that April Time Traveler Recordings reissued Pinnacle for Record Store Day, remastered from the original analog tapes and pressed for the first time since 1975.

The Penguin Guide to Jazz on CD called Williams "one of the key sidemen in modern jazz," crediting him with a firm grounding in harmony, counterpoint, and orchestration, and it is that harmonic command, rather than sheer propulsion, that other bassists tend to name first. His tone is dark, fat, and unforced, and his time is steady enough that four decades of singers, from Nancy Wilson and Sarah Vaughan through Carmen McRae and Shirley Horn, kept calling him back. What distinguishes him from the other first-call bassists of his generation is range: he swings a Muse hard-bop date and plays electric bass through a Moog-heavy sextet with the same conviction, which is why Herbie Hancock could build the Mwandishi band around him and Nancy Wilson could build a nightclub act around him in the same decade. Oscar Pettiford was the model that first made him choose the instrument, and Pettiford's idea of the bass as a solo voice stayed with him: reviewing Houdini in Down Beat, Thomas Conrad described the record as a lesson in how a bassist can move forward in an ensemble without unbalancing it. Williams plays a copy of a late-1800s Panormo, and he has taught the music as well as played it, running a school of his own in Camden since 2013.