Joseph Timothy O'Callahan was a Jesuit priest and, during World War II, a United States Navy chaplain. He was awarded the U.S. military's highest decoration, the Medal of Honor, for his actions during and after an attack on the aircraft carrier aboard which he was serving, USS Franklin.

USS Franklin , nicknamed "Big Ben," was one of 24 Essex-class aircraft carriers built during World War II for the United States Navy, and the fifth US Navy ship to bear the name. Commissioned in January 1944, she served in several campaigns in the Pacific War, earning four battle stars. In March 1945, while launching strikes against the Japanese mainland, she was badly damaged when a single Japanese dive bomber struck her with two bombs. The attack resulted in the loss of 807 of her crew and Franklin became the most heavily-damaged United States aircraft carrier to survive the war. The complement of Franklin suffered 924 killed in action during the war, the worst for any surviving U.S. warship and second only to that of USS Arizona.