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. Fourteen people died: thirteen were killed outright, while the death of another man four months later was attributed to his injuries. 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. The report was widely criticised as a "whitewash". The Saville Inquiry, chaired by Lord Saville of Newdigate, was established in 1998 to reinvestigate the incident much more thoroughly. Following a twelve-year investigation, Saville's report was made public in 2010 and concluded that the killings were "unjustified" and "unjustifiable". It found that all of those shot were unarmed, that none were posing a serious threat, that no bombs were thrown and that soldiers "knowingly put forward false accounts" to justify their firing. The soldiers denied shooting the named victims but also denied shooting anyone by mistake. On publication of the report, British Prime Minister David Cameron formally apologised. Following this, police began a murder investigation into the killings. One former soldier was charged with murder, but the case was dropped two years later when evidence was deemed inadmissible.Bloody Sunday came to be regarded as one of the most significant events of the Troubles because so many civilians were killed by forces of the state, in view of the public and the press. It was the highest number of people killed in a shooting incident during the conflict and is considered the worst mass shooting in Northern Irish history. Bloody Sunday fuelled Catholic and Irish nationalist hostility to the British Army and worsened the conflict. Support for the Provisional Irish Republican Army (IRA) rose, and there was a surge of recruitment into the organisation, especially locally. The Republic of Ireland held a national day of mourning, and huge crowds besieged and burnt down the British Embassy in Dublin.

The Troubles (Irish: Na Trioblóidí) were an ethno-nationalist conflict in Northern Ireland that lasted about 30 years from the late 1960s to 1998. Also known internationally as the Northern Ireland conflict, it is sometimes described as an "irregular war" or "low-level war". The conflict began in the late 1960s and is usually deemed to have ended with the Good Friday Agreement of 1998. Although the Troubles mostly took place in Northern Ireland, at times violence spilled over into parts of the Republic of Ireland, England and mainland Europe.

The conflict was primarily political and nationalistic, fuelled by historical events. It also had an ethnic or sectarian dimension but despite use of the terms 'Protestant' and 'Catholic' to refer to the two sides, it was not a religious conflict. A key issue was the status of Northern Ireland. Unionists and loyalists, who for historical reasons were mostly Ulster Protestants, wanted Northern Ireland to remain within the United Kingdom. Irish nationalists and republicans, who were mostly Irish Catholics, wanted Northern Ireland to leave the United Kingdom and join a united Ireland.

The conflict began during a campaign by the Northern Ireland Civil Rights Association to end discrimination against the Catholic/nationalist minority by the Protestant/unionist government and local authorities. The government attempted to suppress the protests. The police, the Royal Ulster Constabulary (RUC), were overwhelmingly Protestant and accused of sectarianism and police brutality. The campaign was also violently opposed by loyalists, who said it was a republican front. Increasing tensions led to the August 1969 riots and the deployment of British troops, in what became the British Army's longest operation. "Peace walls" were built in some areas to keep the two communities apart. Some Catholics initially welcomed the British Army as a more neutral force than the RUC, but soon came to see it as hostile and biased, particularly after Bloody Sunday in 1972.The main participants in the Troubles were republican paramilitaries such as the Provisional Irish Republican Army (IRA) and the Irish National Liberation Army (INLA); loyalist paramilitaries such as the Ulster Volunteer Force (UVF) and Ulster Defence Association (UDA); British state security forces such as the British Army and RUC; and political activists. The security forces of the Republic of Ireland played a smaller role. Republicans carried out a guerrilla campaign against British forces as well as a bombing campaign against infrastructural, commercial and political targets. Loyalists attacked republicans/nationalists and the wider Catholic community in what they described as retaliation. At times, there were bouts of sectarian tit-for-tat violence, as well as feuds within and between paramilitary groups. The British security forces undertook policing and counter-insurgency, primarily against republicans. There were incidents of collusion between British state forces and loyalist paramilitaries. The Troubles also involved numerous riots, mass protests and acts of civil disobedience, and led to increased segregation and the creation of temporary no-go areas.

More than 3,500 people were killed in the conflict, of whom 52% were civilians, 32% were members of the British security forces and 16% were members of paramilitary groups. Republican paramilitaries were responsible for some 60% of the deaths, loyalists 30% and security forces 10%. The Northern Ireland peace process led to paramilitary ceasefires and talks between the main political parties, which resulted in the Good Friday Agreement of 1998. This Agreement restored self-government to Northern Ireland on the basis of "power-sharing" and it included acceptance of the principle of consent, commitment to civil and political rights, parity of esteem, police reform, paramilitary disarmament and early release of paramilitary prisoners. There has been sporadic violence since the Agreement, including punishment attacks and a campaign by dissident republicans.