< Unsourced image removed: 300px|right|thumb|Jaco Pastorius --> Jaco Pastorius, born John Francis Anthony Pastorius III (December 1, 1951 – September 21, 1987) was a jazz bassist and composer, notable for his virtuoso technique and fretless bass playing style. His influence on the modern electric bass is widely recognized. He was largely responsible for the popularization of the fretless electric bass. He introduced a textural approach and harmonic sense to bass playing that became the signature "Jaco" sound. Jaco's technique and style have profoundly influenced electric bassists in jazz and in other genres. Although he was acclaimed as a virtuoso and a genius, his well-documented offstage disruptions would eventually cost him his life.
Jaco was the first of three sons born to John Francis Pastorius II and Stephanie Katherine Haapala Pastorius. Although Jaco was born in Pennsylvania, the family moved to Fort Lauderdale, Florida when Jaco was very young.