Ponce massacre: Nineteen unarmed civilians in Ponce, Puerto Rico are gunned down by police in a terrorist attack ordered by the US-appointed Governor, Blanton Winship.

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 17 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.

Ponce is a city and a municipality on the southern coast of Puerto Rico. The most populated city outside the San Juan metropolitan area, Ponce was founded on August 12, 1692 and is named after Juan Ponce de León y Loayza, the great-grandson of Spanish conquistador Juan Ponce de León. Ponce is often referred to as La Perla del Sur, La Ciudad Señorial, and La Ciudad de las Quenepas.

Blanton C. Winship was an American military lawyer and veteran of both the Spanish–American War and World War I. During his career, he served both as Judge Advocate General of the United States Army and as the governor of Puerto Rico. An investigation led by the United States Commission on Civil Rights blamed him for the Ponce massacre, which killed 19 people.