The Ponce massacre was an event that took place on Palm Sunday, March 21, 1937, in Ponce, Puerto Rico, when a peaceful civilian march turned into a police shooting in which 19 civilians and two policemen were killed, and more than 200 civilians wounded. None of the civilians were armed and most of the dead were reportedly shot in their backs. The march had been organized by the Puerto Rican Nationalist Party to commemorate the abolition of slavery in Puerto Rico by the governing Spanish National Assembly in 1873, and to protest the U.S. government's imprisonment of the Party's leader, Pedro Albizu Campos, on sedition charges.

An investigation led by the United States Commission on Civil Rights put the blame for the massacre squarely on the U.S.-appointed governor of Puerto Rico, Blanton Winship. Further criticism by members of the U.S. Congress led President Franklin D. Roosevelt to remove Whinship as governor in 1939.

Governor Winship was never prosecuted for the massacre and no one under his chain of command – including the police who took part in the event, and admitted to the mass shooting – was prosecuted or reprimanded.

The Ponce massacre remains the largest massacre in post-Spanish imperial history in Puerto Rico. It has been the source of many articles, books, paintings, films, and theatrical works.