John Francis Anthony Pastorius III was born December 1, 1951, in Norristown, Pennsylvania, to Stephanie Haapala and big-band drummer John Francis Pastorius Jr. The family moved to Oakland Park, near Fort Lauderdale, Florida, when he was eight. He started on drums himself, but a wrist injury from a football game at thirteen forced corrective surgery and pushed him toward the bass; by seventeen he had bought an upright, which promptly cracked in the Florida humidity, so he traded it for a 1962 Fender Jazz Bass. He worked through his teens playing electric bass for R&B bandleader Wayne Cochran and the C.C. Riders, then in the early 1970s taught bass at the University of Miami, where he met guitarist Pat Metheny.

His first significant recording session came June 16, 1974, at Blue Rock Studio in New York, a quartet date led by pianist Paul Bley with Metheny and drummer Bruce Ditmas; it stayed unissued for two years, appearing in 1976 as Pastorius/Metheny/Ditmas/Bley once Pastorius had a name. He also played on Metheny's own ECM debut, Bright Size Life, a trio with drummer Bob Moses recorded in December 1975. His self-titled solo debut, Jaco Pastorius (Epic, 1976), was produced by Blood, Sweat and Tears drummer Bobby Colomby and featured Herbie Hancock (who also wrote the liner notes), Wayne Shorter, Michael Brecker, and Randy Brecker. Tracks like "Portrait of Tracy," built entirely from natural and artificial harmonics, and a virtuoso reworking of Charlie Parker's "Donna Lee" announced a genuinely new vocabulary for the electric bass; the album drew two 1977 Grammy nominations.

Pastorius introduced himself to keyboardist Joe Zawinul after a Weather Report concert in Miami with the line "I'm the greatest bass player in the world," and joined the band for Black Market (1976), sharing bass duties with outgoing member Alphonso Johnson before becoming sole bassist on Heavy Weather (1977), the platinum-selling album that produced the standard "Birdland." He stayed through Mr. Gone (1978), the Grammy-winning 8:30 (1979), Night Passage (1980), and the band's second self-titled album (1982), leaving that year as his own projects and worsening health pulled him away; full details of his tenure and the band's history are in Weather Report's own profile. In between, on March 3, 1979, he joined guitarist John McLaughlin and drummer Tony Williams for a short-lived, high-voltage group billed Trio of Doom, recorded live at the Havana Jam festival in Cuba and then, after a falling-out between Pastorius and Williams during a follow-up studio session in New York five days later, shelved for nearly three decades before Columbia/Legacy issued it in 2007.

Warner Bros. signed Pastorius to lead his own big band, Word of Mouth, whose 1981 studio album of the same name featured Wayne Shorter, Toots Thielemans, and the Brecker brothers among a rotating cast; a 21-piece version of the band toured Japan in 1982, documented on the live album Invitation (1983), recorded at Budokan, Yokohama Stadium, and Osaka's Festival Hall with Peter Erskine on drums and a guest turn from Herbie Hancock. During that Japanese tour Pastorius shaved his head, painted his face black, and threw his bass into Hiroshima Bay, alarming his bandmates; he was diagnosed with bipolar disorder later that year. The rest of the decade brought escalating substance abuse, homelessness, and only intermittent recorded work, though real moments of the old brilliance survived: a December 19, 1984 duo broadcast for French Radio with drummer Rashied Ali, later issued as Blackbird (Timeless/Alfa Jazz, 1991), and a 1986 studio pairing with young guitarist Biréli Lagrène released as Stuttgart Aria.

Pastorius passed away on September 21, 1987, in Fort Lauderdale, ten days after being severely beaten by a nightclub employee, Luc Havan, following an altercation outside the Midnight Bottle Club; he never regained consciousness after the assault fractured his skull and face. He was 35. He was inducted into the DownBeat Hall of Fame in 1988, the only electric bassist in the Hall as of the mid-2010s, and his original 1962 Jazz Bass, nicknamed the Bass of Doom, was eventually restored and returned to his family with help from Metallica's Robert Trujillo.

Pastorius did not just play the electric bass well; he changed what the instrument was understood to do. He stripped the frets from his 1962 Fender Jazz Bass, coated the fingerboard in epoxy, and used the resulting fretless voice to carry melody and countermelody the way a horn or a guitar would, layering in chordal harmonics, Motown- and James Jamerson-inflected funk syncopation, and Afro-Cuban rhythmic phrasing learned growing up in South Florida. On stage he brought a showman's instinct closer to Jimi Hendrix than to any bassist before him, playing loud and fast, singing, dancing, and performing publicly with a physicality the instrument had never invited. Bass Player magazine later ranked him second only to Jamerson among the greatest electric bassists in history, and his influence runs directly through a generation of rock, metal, and fusion players, including Flea of the Red Hot Chili Peppers, Metallica's Robert Trujillo, and Rush's Geddy Lee. Within jazz, his blend of virtuosity and compositional ambition, heard as much in his writing for the Word of Mouth big band as in his solos, made him as influential a bandleader-in-miniature as a sideman.