James Aloysius Johnston (September 15, 1874 – September 7, 1954) was an American politician and prison warden who served as the first and longest-serving warden of Alcatraz Federal Penitentiary, serving from 1934 to 1948. He had earlier served as wardens of California state prisons at Folsom (1912-1913) and San Quentin (1914-1924).