John Francis Anthony “Jaco” Pastorius III (/ˈdʒɑːkoʊ pæˈstɔːriəs/, December 1, 1951 – September 21, 1987) was an American jazz bassist who was a member of Weather Report from 1976 to 1981. He worked with Pat Metheny and Joni Mitchell, and recorded albums as a solo artist and band leader. His bass playing employed funk, lyrical solos, bass chords, and innovative harmonics. As of 2017, he is the only electric bassist of seven bassists inducted into the DownBeat Jazz Hall of Fame, and has been lauded as one of the best electric bassists of all time.

Pastorius suffered from drug addiction and mental health problems throughout his professional life, and despite his widespread acclaim had problems over the latter part of his life holding down jobs due to his unreliability. In frequent financial trouble, he was often homeless throughout the mid 1980s. In 1987, he got into a fight outside of a music club in South Florida and died as result of injuries sustained in the fight. He was only 35 years old.

After his death, his work continued to influence musicians, being elected to the DownBeat Hall of Fame in 1988. He was the subject of the 2014 documentary film Jaco.

John Francis Pastorius was born December 1, 1951, in Norristown, Pennsylvania. He was the oldest of three boys born to Stephanie, his Finnishmother, and Jack Pastorius, a charismatic singer and jazz drummer who spent much of his time on the road. His family moved to Oakland Park in Fort Lauderdale when he was eight.

By 1968–1969, at the age of 17, Pastorius had begun to appreciate jazz and had saved enough money to buy an upright bass. Its deep, mellow tone appealed to him, though it strained his finances. He had difficulty maintaining the instrument, which he attributed to the humidity in Florida. When he woke one day to find it had cracked, he traded it for a 1962 Fender Jazz Bass. In his teens he played bass guitar for Wayne Cochran and the C.C. Riders.

In the early 1970s, Pastorius taught bass at the University of Miami, where he befriended jazz guitarist Pat Metheny, who was also on the faculty. With Paul Bley, Pastorius and Metheny recorded an album, later titled Jaco (Improvising Artists, 1974). Pastorius then played on Metheny’s debut album, Bright Size Life(ECM, 1976). He recorded his debut solo album, Jaco Pastorius (Epic, 1976) with Michael Brecker, Randy Brecker, Herbie Hancock, Hubert Laws, Pat Metheny, Sam & Dave, David Sanborn, and Wayne Shorter. Before recording his debut album, Pastorius attended a concert in Miami by the jazz fusion band Weather Report. After the concert, he approached keyboardist Joe Zawinul, who led the band. As was his habit, he introduced himself by saying, “I’m John Francis Pastorius III. I’m the greatest bass player in the world.”Zawinul admired his brashness and asked for a demo tape. After listening to the tape, Zawinul realized that Pastorius had considerable skill. They corresponded, and Pastorius sent Zawinul a rough mix of his solo album.

After bassist Alphonso Johnson left Weather Report, Zawinul asked Pastorius to join the band. Pastorius made his band debut on the album Black Market(Columbia, 1976), in which he shared the bass chair with Johnson. Pastorius was fully established as sole band bass player for the recording of Heavy Weather(Columbia, 1977), which contained the Grammy-nominated hit “Birdland“.