John William Casady (born April 13, 1944) is an American bass guitarist, best known as a member of Jefferson Airplane and Hot Tuna. Jefferson Airplane became the first successful exponent of the San Francisco Sound. Singles including "Somebody to Love" and "White Rabbit" charted in 1967 and 1968. Casady, along with the other members of Jefferson Airplane, was inducted into the Rock and Roll Hall of Fame in 1996.

Casady became the bass player for Jefferson Airplane when lead guitarist Jorma Kaukonen, a high school friend and former Triumphs rhythm guitarist, invited him to join in late September 1965. He replaced the band's original bassist Bob Harvey the following month.