Mary Heaton Vorse or Mary Heaton Vorse O'Brien (1874–1966) was an American journalist, labor activist, and novelist. Vorse was outspoken and active in peace and social justice causes, such as women's suffrage, civil rights, pacifism (specifically including opposition to World War I), socialism, child labor, infant mortality, labor disputes, and affordable housing.
Mary Heaton Vorse was born October 11, 1874 in New York City. She was raised in prosperity in Amherst, Massachusetts in a 24-room house, tended by nurses and housemaids. The money in her family came from her mother's side, her mother having married a wealthy shipping magnate and liquor merchant more than 20 years her senior when she was a young woman of 18. Her mother had been widowed at age 37 and had soon married again to Mary's father, Hiram Heaton.