200px-IRA Volunteers 1979

Masked Provisional IRA volunteers at a rally in August 1979

The Provisional Irish Republican Army (IRA) is an Irish republican paramilitary organisation whose aim was to remove Northern Ireland from the United Kingdom and bring about a united Ireland by force of arms and political persuasion. It emerged out of the December 1969 split of the Irish Republican Army due to differences over ideology and over how to respond to violence against the nationalist community. This violence had followed the community's demands for civil rights in 1968 and 1969, which met with resistance from the unionist community and from the authorities, and culminated in the 1969 Northern Ireland riots. The IRA conducted an armed campaign, primarily in Northern Ireland but also in England, over the course of which is believed to have been responsible for the deaths of approximately 1,800 people. The dead included around 1,100 members of the British security forces, and about 630 civilians. The IRA itself lost 275 – 300 members, of an estimated 10,000 total over the thirty-year period. The Provisional Irish Republican Army is also referred to as the PIRA, the Provos, or by its supporters as the Army or the 'RA; its constitution establishes it as Óglaigh na hÉireann ("The Irish Volunteers") in the Irish language.

The IRA's initial strategy was to use force to cause the collapse of the Northern Ireland administration and to inflict enough casualties on the British forces that the British government would be forced by public opinion to withdraw from the region. This policy involved recruitment of volunteers, increasing after Bloody Sunday, and launching attacks against British military and economic targets. The campaign was supported by arms and funding from Libya and from some groups in the United States. The IRA agreed to a ceasefire in February 1975, which lasted nearly a year before the IRA concluded that the British were drawing them into politics without offering any guarantees in relation to the IRA's goals, and hopes of a quick victory receded. As a result, the IRA launched a new strategy known as "the Long War". This saw them conduct a war of attrition against the British and increase emphasis on political activity, via Sinn Féin.

The success of the 1981 Irish hunger strike in mobilising support and winning elections led to the Armalite and ballot box strategy with more time and resources devoted to political activity. The abortive attempt at an escalation of the military part of that strategy led republican leaders increasingly to look for a political compromise to end the conflict, with a broadening dissociation of Sinn Féin from the IRA. Following negotiations with the SDLP and secret talks with British civil servants, the IRA ultimately called a ceasefire in 1994 on the understanding that Sinn Féin would be included in political talks for a settlement. When this did not happen, the IRA called off its ceasefire from February 1996 until July 1997, carrying out several bombing and shooting attacks. These included the Docklands bombing and the Manchester bombing, which together caused around £500 million in damage. After the ceasefire was reinstated, Sinn Féin was admitted into all-party talks, which produced the Belfast Agreement of 1998.

On 28 July 2005, the IRA Army Council announced an end to its armed campaign, stating that it would work to achieve its aims using "purely political and democratic programmes through exclusively peaceful means", and shortly afterwards completed decommissioning. In September 2008, the nineteenth report of the Independent Monitoring Commission stated that the IRA was "committed to the political path" and no longer represented "a threat to peace or to democratic politics", and that the IRA's Army Council was "no longer operational or functional". The organisation remains classified as a proscribed terrorist group in the UK and as an illegal organisation in the Republic of Ireland. Two small groups split from the Provisional IRA, first in 1986 (Continuity IRA) and then in 1997 (Real IRA). Both reject the Belfast Agreement and continue to engage in violence.