John Joseph Edward "Jack" Cassidy (March 5, 1927 - December 12, 1976) was an American actor who achieved success in theater, cinema and television.

Born in Queens, New York, Cassidy achieved his greatest success as a musical performer on Broadway, winning a Tony Award for his role in She Loves Me . He also received Emmy Award nominations for his television performances in He & She (1967) and The Andersonville Trial (1970). On television he became a frequent guest, appearing in such programs as Bewitched, Get Smart, Hawaii Five-O and McCloud. He turned down the role of Ted Baxter in The Mary Tyler Moore Show, appearing instead as Baxter's brother Hal.

He was married twice. His first wife was actress Evelyn Ward, who is the mother of his son David. After divorcing Evelyn Ward in 1956, he married actress Shirley Jones, whom he divorced in 1974. They had three sons: Shaun, Patrick , and Ryan Cassidy.

He died from burns received in a fire he caused by smoking in bed, in West Hollywood, California.