John Joseph McGrath (July 23, 1872 – August 25, 1951) was an Irish-American politician who served as a U.S. Representative from California for three terms from 1933 to 1939.

He was educated at the Christian Brothers College in Cork and immigrated to the United States at the age of seventeen, living initially in Chicago.

He studied law briefly and worked as a salesman and sales manager for many years, becoming a U.S. citizen in 1896.

He served three full terms from 1933 to 1939, but was defeated for re-election in 1938 by Republican Jack Z. Anderson.

Subsequently, he served as commissioner for immigration and naturalization in San Francisco from 1939 to 1940 before retiring.