Leonard James Callaghan was born at 38 Funtington Road, Copnor, Portsmouth, England, on 27 March 1912. He took his middle name from his father, James (1877–1921), who was the son of an Irish Catholic father who had fled to England during the Great Irish Famine, and a Jewish mother. Callaghan's father ran away from home in the 1890s to join the Royal Navy; as he was a year too young to enlist, he gave a false date of birth and changed his surname from Garogher to Callaghan, so that his true identity could not be traced. He rose to the rank of Chief Petty Officer.