File:Troubles both sides.jpg
The two sides involved in the Troubles.
Northern Ireland still suffers from its past, and it will take generations to escape sectarianism and for violence to end totally. Nonetheless, it is in a different place now than during the Troubles, and it will not go back to the old days.
~ Jonathan Powell

The Troubles (Irish: Na Trioblóidí) was an ethno-nationalist/sectarian period of conflict in Northern Ireland that lasted about 30 years from the late 1960s to the late 1990s. Also known internationally as the Northern Ireland conflict, it is sometimes described as a civil war, while at other times has been 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 the 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 the use of the terms "Protestant" and "Catholic" to refer to the two sides, it was not a religious conflict. A key issue was the constitutional status of Northern Ireland. Unionists, who were mostly Ulster Protestants, wanted Northern Ireland to remain within the United Kingdom. Irish nationalists, 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 of Northern Ireland and Royal Ulster Constabulary (RUC). The authorities attempted to suppress the protest campaign with police brutality; it was also met with violence from loyalists, who believed it was a republican front. Increasing tensions led to severe violence in August 1969 and the deployment of British troops, in what became the British Army's longest ever 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 it soon came to be seen 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—the British Army and RUC; and political activists and politicians. The security forces of the Republic of Ireland played a smaller role. Other involved organizations included the Irish People's Liberation Organization (IPLO) and Ian Paisley's Democratic Unionist Party.

The more violent actions during the Troubles were often carried out by smaller street gangs (described as "death squads" by some), such as the Shankill Butchers (made up of UVF members) and the Balcombe Street Gang (made up of Provisional IRA members.) These gangs carried out acts of torture, kidnapping, and mutilation, and often carried out smaller acts of lone-wolf terrorism and mass shootings.

Republican paramilitaries carried out a terrorist guerrilla campaign against British security forces as well as a bombing campaign against infrastructural, commercial and political targets. Loyalists targeted republicans/nationalists and attacked 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 of the same stripe. The British security forces undertook both a policing and counter-insurgency role, primarily against republicans. There was extensive collusion between British security 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%. There has been sporadic violence since the Good Friday Agreement was signed in 1998, including ongoing punishment attacks and a campaign by dissident republicans to achieve a United Ireland.