John Leroy "Johnny" Heartsman (February 9, 1936 – December 27, 1996) was an American electric blues and soul blues musician and songwriter. He showed musical diversity, playing a number of musical instruments, including the electronic organ and flute. He contributed his distinctive guitar playing to a number of recordings made in the San Francisco Bay Area in the 1950s and 1960s. He continued playing until his death.
His best-known recording, "Johnny's House Party", was an R&B hit in 1957. Other notable tracks recorded by Heartsman are "Paint My Mailbox Blue" and "Heartburn". He variously worked with Jimmy McCracklin, Sugar Pie DeSanto, Big Mama Thornton, Ray Agee, Jimmy Wilson, Johnny Fuller, Al King, Tiny Powell and Joe Simon.
He is not to be confused with the American jazz singer Johnny Hartman.