Ireland has been divided administratively since 1922 when the Irish Free State was formed
Key events in Northern Ireland history:
12th century: First involvement by England in Irish affairs when the Earl of Pembroke, known as Strongbow, intervenes in a local dispute in Leinster in 1170 . King Henry II lands the following year.
English expansion continues and in 1177, Ulster is conquered by soldiers led by John de Courcy.
14th/15th centuries English expansion halted and then reversed. By the end of the period, English possessions are limited to a small area around Dublin. the 'Pale'. Everything outside is regarded as savage, giving rise to the expression 'beyond the pale'.
16th century First Henry VIII and then Elizabeth I take an increasing interest in Ireland. Colonisation increases again, sparking off several rebellions late in the century.
The greatest of the revolts, led by Ulsterman Hugh O'Neill, the Earl of Tyrone, reaches its high point with victory over the English at the Yellow Ford in 1598, but he is defeated three years later at Kinsale and surrenders.
17th century Start of the 'Plantation of Ulster' - the systematic colonisation of Donegal, Tyrone, Derry, Armagh, Cavan and Fermanagh by settlers from England and Scotland.
After Parliament's victory in the English civil war, Oliver Cromwell conquered the whole of Ireland and set about opening the island up to colonisation.
1690 Protestant King William of Orange's troops defeated the Catholic army of King James at the Battle of the Boyne to confirm his claim to the English throne and with it Ireland.
By the end of the 17th century, Ulster in particular was heavily settled, mainly by Scottish Presbyterians.
1912 Amid a growing home rule campaign, the Ulster Unionist leader, Sir Edward Carson, sets up the original Ulster Volunteer Force as a bulwark against Dublin's domination of the Protestant-majority 'six counties' in the north of Ireland. Carson is still regarded by many as the founder of the state of Northern Ireland.
1916 The Easter Rising. Pro-home rule Irish rebels seize the Post Office building in the centre of Dublin but are eventually ousted by British soldiers. Fifteen of the rebellion's leaders are executed. Carson's UVF, which had become a division of the British Army, fights in France and a thousand die at the Somme.
1921-22 The first Northern Ireland Parliament opens
After a long and bitter guerrilla campaign against the British Army, Ireland is granted partial home rule.
The Irish Free State is set up in the southern 26 counties of Ireland. Its architect, Michael Collins, is assassinated during the ensuing civil war between his Free State forces and the IRA, which refuses to accept the partition.
The war ends after the new Irish Government executes IRA leaders.
1939-45 Irish Republic remains neutral in World War II while Northern Ireland becomes an important Allied sea and air base.
1949 Ireland becomes a full republic and the British government gives new constitutional guarantees to the Northern Ireland Parliament at Stormont.
1952 The Official IRA calls off a series of attacks on Royal Ulster Constabulary police stations near the Irish border which cause few casualties and generated little publicity.
1956 The IRA launches a border campaign which leads to the introduction of internment of suspects without trial both in the Republic and in Northern Ireland.
1968 The civil rights movement begins the campain for equal rights in housing and voting for poorer Catholics. Protestants counter-demonstrate.
1969 March:The RUC is armed in border areas for the first time since 1965.
August: The province's Catholic minority welcomes British troops, sent to Northern Ireland in response to an upsurge in sectarian violence. The Provisional IRA (the 'Provos') breaks away from the Official IRA, which is criticised for failing to protect Catholic enclaves.
1970 August: The Social Democratic and Labour Party (SDLP) is formed to press for Catholic civil rights. By now the British Army is being seen as an army of occupation by many Catholics and several soldiers are shot dead by the IRA.
October: The former Irish Finance Minister, Charles Haughey, is found not guilty of illegally importing arms. It was alleged he planned to send the weapons across the border to arm nationalists. Mr Haughey, later to become Prime Minister of the Republic, becomes a hate figure for Unionists in Northern Ireland.
1971 February: First soldier shot dead in Northern Ireland since troops arrived in August 1969.
August: Internment without trial is introduced. Hundreds of suspected extremists, including the present Sinn Fein President, Gerry Adams, are rounded up and detained over the next four years.
December: 15 people are killed in an attack on a Belfast pub. The Ulster Volunteer Force claims responsibility.
1972 Thirteen catholics were shot dead by British troop on 'Bloody Sunday'
January: 'Bloody Sunday': Thirteen Catholic protesters die after being shot by troops from the 1st Battalion the Parachute Regiment following disturbances during a banned civil rights march in Londonderry.
March: Edward Heath's Conservative government imposes direct rule on the province, creating the post of Northern Ireland Secretary, and closes the Unionist-dominated Stormont Parliament in a concession to republicans. The Ulster Unionist Party breaks off formal links with the Conservative Party in protest.
The IRA declares a temporary ceasefire and several republican leaders, including Gerry Adams, are flown to London for secret talks with the Government, which come to nothing.
July: Nine people are killed when 22 bombs explode in Belfast. This became known as 'Bloody Friday'. The IRA was held responsible.
1974 January: The Government sets up a power-sharing executive, in which posts are handed out on a quota basis, in a bid to include Catholics in the decision-making process and end the much-resented Unionist domination.
May: In Dublin, 22 people are killed by car bombs which explode without warning. Five people are killed by a car bomb in Monaghan Town. Three more people die later from their injuries. Loyalist paramilitaries are thought to have carried out the attacks, although the UDA and the UVF deny they were involved.
Protestant workers all over Northern Ireland go on strike in protest at the power-sharing executive plus a proposed council of all Ireland. It promptly resigns and direct rule is reimposed.
October: Five people killed as IRA bomb wrecks a pub in Guildford, Surrey, frequented by soldiers. IRA attacks another pub also used by soldiers in Woolwich, south east London.
November: Twenty-one people killed by two IRA bombs planted in two pubs in Birmingham.
1975 October: In a series of UVF attacks, 12 people are killed and 46 people injured. The UVF is declared an illegal organisation.
November: A gang of loyalists, known as the Shankill Butchers, abduct and murder a Catholic reveller as he walks home through west Belfast.
December: Internment is lifted by the new Northern Ireland Secretary, Labour's Merlyn Rees.
1977 May: The Second Ulster (Protestant) Workers' Strike peters out.
1978 February: 12 people are killed and 23 injured in an IRA bomb attack on a hotel in County Down.
1979 Charles Haughey is elected Taoiseach of the Republic (Prime Minister).
Eleven members of the so-called 'Shankill Butchers', are given life sentences by a Belfast court for a series of sectarian murders.
March: Airey Neave, Conservative MP and shadow Northern Ireland Secretary, is killed by a bomb attached to his car in the House of Commons car park by the Irish National Liberation Army (INLA), the military wing of the Irish Republican Socialist Party, an IRA splinter group.
August: Lord Mountbatten, last Viceroy of India and uncle of the Prince of Wales, is killed by an IRA bomb on his boat off the coast of County Donegal in the Irish Republic. On the same day an IRA bomb explodes under an Army bus at Warrenpoint, County Down. A second bomb goes off as the survivors clamber out of the bus and onto an Army helicopter.
Eighteen soldiers and one civilian die. It is the Army's biggest single setback since the IRA campaign began.
1981 Bobby Sands became a republican martyr in 1981
May: Bobby Sands dies in the Maze Prison after a prolonged hunger strike. He is the first of 10 IRA and INLA prisoners to starve to death. They were protesting, in vain, for the right to be considered prisoners of war rather than criminals.
1984 October: Five people are killed and 30 injured when an IRA bomb explodes at the Grand Hotel in Brighton during the Conservative Party conference. The Conservative Prime Minister, Margaret Thatcher, narrowly escapes death and the party Chairman, Norman Tebbit, is seriously injured.
1985 November: The Anglo-Irish Agreement is signed by Mrs Thatcher and the Irish Taoiseach, Garret FitzGerald, setting up a number of cross-border initiatives. It is opposed by many Ulster unionists. Thousands turn out in Belfast to cheer Reverend Ian Paisley's famous 'No Surrender' speech against the agreement.
1987 November: Eleven killed by an IRA bomb which explodes during a Remembrance Service in Enniskillen, County Fermanagh.
1988 March: Three IRA members are shot dead by British special forces in Gibraltar, where they are allegedly planning an attack on the British garrison.
Nine days later, during their funeral, a lone loyalist gunman, Michael Stone, kills three mourners in a gun and grenade attack on the Milltown cemetery in west Belfast.
Four days later two soldiers in civilian clothes drive into the funeral cortege of one of the IRA men killed by Stone and are abducted, beaten, stripped and shot dead.
1989 September: Eleven army bandsmen are killed when a bomb explodes at the Royal Marines School of Music in Deal, Kent.
1990 July: Conservative MP Ian Gow, a strong supporter of the unionist cause, is murdered by an IRA bomb at his Sussex home.
1992 April: An IRA bomb outside the Baltic Exchange building in the City of London kills three.
1993 March: Two children, aged three and 12, are killed by an IRA bomb planted in a rubbish bin in the centre of Warrington, Cheshire.
October: Loyalist gunmen storm into the Rising Sun bar in Greysteel, County Londonderry shouting "trick or treat" and open fire on drinkers, killing six men and two women.
1994 July: Several people, including a man in his 80s are shot by loyalist gunmen as they watch the Ireland v Italy World Cup match on television in a pub in the predominantly Catholic village of Loughinisland, County Down.
August: IRA announces a complete cessation of violence.
October: cessation of loyalist hostilities announced by the Combined Loyalist Military Command.
1995 US President Bill Clinton shakes hands with Gerry Adams
December: President Clinton visits Northern Ireland and shakes hands with Gerry Adams.
1996 February: The IRA calls off its ceasefire and one hour later sets off a bomb at South Quay near Canary Wharf in London's Docklands which kills two, injures 100 and causes millions of pounds' worth of damage.
The Docklands bomb brought to an end the first IRA ceasefire
A few days later another bomb explodes prematurely on a bus in Aldwych, central London, killing eight people including the bomber.
June: A huge IRA bomb destroys Manchester's Arndale Centre but no-one is killed.
July: A march by Orangemen is blocked by the RUC at Drumcree, near Portadown, as it approaches the Catholic Garvaghy Road area. After a stand-off, the RUC then makes a U-turn and permits the march, sparking violent clashes between Catholics and the police in Portadown, Belfast and Londonderry.
A few days later 40 people are injured by a bomb at the Killyhevlin Hotel in Enniskillen. Responsibility is claimed by the extremist republican Continuity Army Council.
August: Northern Ireland Secretary Sir Patrick Mayhew bans loyalist Apprentice Boys from marching along contentious sections of Londonderry's city walls for the traditional Siege of Derry celebration. Loyalist leaders pull back from a confrontation with security forces.
October: An IRA bomb explodes at the Thiepval Barracks in Lisburn, killing a British soldier.
1997 February: Corporal Stephen Restorick is shot dead by an IRA sniper at a checkpoint in south Armagh.
April: IRA bomb hoaxers cause havoc on Britain's motorways, especially the M6 in Birmingham and the M1 in Northamptonshire.
July: IRA declares another ceasefire. UUP leader David Trimble meets Tony Blair in Downing Street. At a news conference afterwards, Mr Trimble announces that the Unionists are unhappy with the talks proposals and will not support the Government on the decommissioning vote. Ian Paisley meets Tony Blair and claims the talks process was 'dead in the water'. First Sinn Fein-Government meeting since the restoration of the IRA ceasefire.
August: Gerry Adams and Mo Mowlam (Northern Ireland Secretary) meet at Stormont for the first time since the ceasefire. Mo Mowlam announces that Sinn Fein will be admitted to the peace talks.
September: Sinn Fein affirms its commitment to the Mitchell principles of democracy and non violence but the Unionists remain unconvinced. These guidelines are named after the former American senator George Mitchell who chairs the political talks process. The six principles include the total disarmament of all paramilitary organisations and the end of the so-called punishment killings and beatings.
The deadlock is broken as the parties concerned strike a deal opening the way to peace talks.
October: For the first time in 25 years unionists, loyalists, nationalists and republicans sit together to seek a solution to Ulster's problems. Tony Blair shakes hands with Sinn Fein's Martin McGuinness and Gerry Adams. He becomes the first British Prime Minister for 70 years to meet a Sinn Fein delegation. Unionists react angrily.
The Ulster Freedom Fighters (UFF) withdraw from the Combined Loyalist Military Command, the umbrella group for loyalist paramilitary groups.
The Northern Ireland Secretery Mo Mowlam gives wider powers to the Northen Ireland Parades Commission. The intention is to halt or re-route flashpoint marches. Nationalist residents groups called for the disbandment of the commission.
December: Gerry Adams and Sinn Fein delegation meet Prime Minister Tony Blair at Number 10 Downing Street, he is the first Irish Republican leader to visit Downing Street since Michael Collins visited Lloyd George in 1921.
Londonderry experiences its worst violence since the restoration of the IRA ceasefire in July, when riots break out as nationalists protest at a Protestant Apprentice Boys parade through the city centre.
The Northern Ireland Secretary orders a full inquiry into how a republican prisoner managed to escape from the high-security Maze prison despite the recent tightening of security.
Billy Wright, one of Ulster's most feared loyalist paramilitaries, is shot dead at the top security Maze prison in Northern Ireland. His Loyalist Volunteer Force carry out a series of revenge shootings - one within 24 hours and another on New Year's Eve.
1998 January: The peace process is in danger of collapsing as loyalist prisoners in the Maze withdraw their support for the talks.
Mo Mowlam gambles on a historic face-to-face meeting with the prisoners inside the Maze. It works and the loyalist inmates announce renewed support for the peace process. Two days later another Catholic is murdered by LVF gunmen. The victim, Terry Enwright, is married to a niece of Gerry Adams.
After a period of violence in which a total of seven Catholics and two Protestants die, the loyalist Ulster Democratic Party leaves the peace talks when one of the groups to which it is linked, the Ulster Freedom Fighters, admits some of the killings.
February: Two men are killed and the IRA is blamed by RUC chief constable Ronnie Flanagan. As a result, Sinn Fein is suspended from the peace talks until March 9 despite arguing that it does not represent the IRA. Sinn Fein says it might not return to the table and insists on a meeting with Tony Blair.
The UDP is readmitted to the talks after its suspension is lifted.