From 1969 until 1997, the Provisional Irish Republican Army (IRA) conducted an armed paramilitary campaign primarily in Northern Ireland and England, aimed at ending British rule in Northern Ireland in order to create a united Ireland.The Provisional IRA emerged from a split in the Irish Republican Army in 1969, partly as a result of that organisation's perceived failure to defend Catholic neighbourhoods from attack in the 1969 Northern Ireland riots. The Provisionals gained credibility from their efforts to physically defend such areas in 1970 and 1971. From 197172, the IRA took to the offensive and conducted a relatively high-intensity campaign against the British and Northern Ireland security forces and the infrastructure of the state. The British Army characterised this period as the "insurgency phase" of the IRA's campaign.

The IRA declared a brief ceasefire in 1972 and a more protracted one in 1975, when there was an internal debate over the feasibility of future operations. The armed group reorganised itself in the late 1970s into a smaller, cell-based structure, which was designed to be harder to penetrate. The IRA then carried out a smaller scale but more sustained campaign, which they characterised as the 'Long War', with the eventual aim of weakening the British government's resolve to remain in Ireland. The British Army called this the "terrorist phase" of the IRA's campaign.

The IRA made attempts in the 1980s to escalate the conflict with the aid of weapons donated by Libya. In the 1990s they also resumed a campaign of bombing economic targets in London and other cities in England.

On 31 August 1994, the IRA called a unilateral ceasefire with the aim of having their associated political party, Sinn Fin, admitted into the Northern Ireland peace process. The organisation ended its ceasefire in February 1996 but declared another in July 1997. The IRA accepted the terms of the Good Friday Agreement in 1998 as a negotiated end to the Northern Ireland conflict. In 2005 the organisation declared a formal end to its campaign and had its weaponry decommissioned under international supervision.

Other aspects of the Provisional IRA's campaign are covered in the following articles:

For a chronology, see Chronology of Provisional IRA actions

For the Provisional IRA's armament, see Provisional IRA arms importation

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.