William Ladd (1778–1841) was an American anti-war activist.
William Ladd may also refer to:
William E. Ladd (1880–1967), American surgeon William F. Ladd (1896–1980), American major general William Ladd Taylor (1854–1926), American illustrator William Palmer Ladd (1870–1941), American Episcopal priest and scholar William S. Ladd (1826–1893), American politician and businessman SS William S. Ladd, an American Liberty ship