Harrison was born March 12, 1925, as Henry Maxwell Dempsey in Stamford, Connecticut. His father, Henry Leo Dempsey, a printer who was three-fourths of Irish descent, changed his name to Harrison soon after Harry was born. Harry did not know this himself until he was 30 years old, at which point he changed his name to Harry Max Harrison in court. His mother, Ria H. (Kirjassoff), was Russian Jewish. She had been born in Riga, Latvia, and grew up in St. Petersburg, Russia. Her brother, Max David Kirjassoff (1888-1923), had been an American consul in Japan, but he died along with his wife Alice during the 1923 Great Kantō earthquake in 1923.