Bloody Sunday, or the Bogside Massacre, was a massacre on 30 January 1972 when British soldiers shot 26 unarmed civilians during a protest march in the Bogside area of Derry, Northern Ireland. Thirteen men were killed outright and the death of another man four months later was attributed to gunshot injuries from the incident. Many of the victims were shot while fleeing from the soldiers, and some were shot while trying to help the wounded. Other protesters were injured by shrapnel, rubber bullets, or batons; two were run down by British Army vehicles; and some were beaten. All of those shot were Catholics. The march had been organised by the Northern Ireland Civil Rights Association (NICRA) to protest against internment without trial. The soldiers were from the 1st Battalion of the Parachute Regiment ("1 Para"), the same battalion implicated in the Ballymurphy massacre several months before.

Two investigations were held by the British government. The Widgery Tribunal, held in the aftermath, largely cleared the soldiers and British authorities of blame. It described some of the soldiers' shooting as "bordering on the reckless", but accepted their claims that they shot at gunmen and bomb-throwers.