Belfast is the capital and largest city of Northern Ireland, standing on the banks of the River Lagan on the east coast. It is the 12th-largest city in the United Kingdom and the second-largest on the island of Ireland. It had a population of 343,542 as of 2019. Belfast suffered greatly during the violence that accompanied the partition of Ireland, and especially during the more recent conflict known as the Troubles: in the 1970s and 1980s it was one of the world's most dangerous cities, with a homicide rate around 31 per 100,000.

The county borough of Belfast was created when it was granted city status by Queen Victoria in 1888, and the city continues to straddle County Antrim and County Down.

The site of Belfast has been occupied since the Bronze Age. The Giant's Ring, a 5,000-year-old henge, is located near the city, and the remains of Iron Age hill forts can still be seen in the surrounding hills. Belfast remained a small settlement of little importance during the Middle Ages. John de Courcy built a castle on what is now Castle Street in the city centre in the 12th century, but this was on a lesser scale and not as strategically important as Carrickfergus Castle to the north, which was built by de Courcy in 1177. The O'Neill clan had a presence in the area.

In the 14th century, Cloinne Aodha Buidhe, descendants of Aodh Buidhe O'Neill, built Grey Castle at Castlereagh, now in the east of the city. Conn O'Neill of the Clannaboy O'Neills owned vast lands in the area and was the last inhabitant of Grey Castle, one remaining link being the Conn's Water river flowing through east Belfast.

The Early Town

Belfast became a substantial settlement in the 17th century after being established as an English town by Sir Arthur Chichester. As it grew with the port, and with textile manufacture, the English element was overwhelmed by the influx of Scottish Presbyterians. As "Dissenters" from the established Church of Ireland communion, the Presbyterians were conscious of sharing, if only in part, the disabilities of Ireland's largely dispossessed Roman Catholic majority.

When, in the American War of Independence, Belfast Lough was raided by the privateer, John Paul Jones, the townspeople assembled their own Volunteer militia. This emboldened a spirit a radical disaffection. Further enthused by the French Revolution, the Volunteers and townspeople rallied in support of Catholic emancipation and "a more equal representation of the people" in the Irish Parliament. The two MPs Belfast returned to Dublin had remained nominees of the Chichesters (Marquesses of Donegall). In the face of the Ascendancy's intransigence, these were demands taken up by the Society of United Irishmen formed at a meeting in the town addressed by Theobald Wolfe Tone. In the expectation of French assistance the Society organised a republican insurrection, defeated to the north and south of Belfast, at Antrim and Ballynahinch, in 1798.

Evidence of this period of Belfast's growth can still be seen in the oldest areas of the city, known as the Entries.

The Industrial City

Rapid industrial growth in the nineteenth century drew in landless Catholics from outlying rural and western districts, most settling to the west of the town. The plentiful supply of cheap labour helped attract the English and Scottish capital to Belfast, but it was also a cause of insecurity. Protestant workers organised to protect "their" jobs giving a new lease of life in the town to the once largely rural Orange Order. Sectarian tensions were heightened by movements to repeal the Acts of Union and to restore a Parliament in Dublin. Given the progressive enlargement of the British electoral franchise, this would have had an overwhelming Catholic majority and, it was widely believed, interests inimical to the Protestant and industrial north. In 1864 and 1886 the issue had helped trigger deadly sectarian riots.

Sectarian tension was not in itself unique to Belfast: it was shared with Liverpool and Glasgow, cities that following the Great Famine had also experienced large scale Irish Catholic immigration. But also common to this "industrial triangle" were traditions of labour militancy. In 1919, workers in all three cities struck for a ten-hour reduction in the working week. In Belfast—notwithstanding the political friction caused by Sinn Féin's electoral triumph in the south—this involved some 60,000 workers, Protestant and Catholic, in a four-week walk-out.

In a demonstration of their resolve not to submit to a Dublin parliament, in 1912 Belfast City Hall unionists presented the Ulster Covenant, which, with an associated Declaration for women, was to accumulate over 470,000 signatures. This was followed by the drilling and eventual arming of a 100,000 strong Ulster Volunteer Force. The crisis was abated by the onset of the Great War, the sacrifices of the UVF in which continue to be commemorated in the city (Somme Day) by unionist and loyalist organisations.

In 1921, as the greater part of Ireland seceded as the Irish Free State, Belfast became the capital of the six counties remaining as Northern Ireland in the United Kingdom. In 1932 the devolved parliament for the region was housed in new buildings at Stormont on the eastern edge of the city. In 1920–21, as the two parts of Ireland drew apart, up to 500 people were killed in disturbances in Belfast, the bloodiest period of strife in the city until the Troubles of the late 1960s onwards.

Belfast was heavily bombed during World War II. Initial raids were a surprise as the city was believed to be outside of the range of German bomber planes. In one raid, in 1941, German bombers killed around one thousand people and left tens of thousands homeless. Apart from London, this was the greatest loss of life in a night raid during the Blitz.

The Troubles

Belfast has been the capital of Northern Ireland since its establishment in 1921 following the Government of Ireland Act 1920. It had been the scene of various episodes of sectarian conflict between its Catholic and Protestant populations. These opposing groups in this conflict are now often termed republican and loyalist respectively, although they are also loosely referred to as 'nationalist' and 'unionist'. The most recent example of this conflict was known as the Troubles – a civil conflict that raged from around 1969 to 1998.

Belfast saw some of the worst of the Troubles in Northern Ireland, particularly in the 1970s, with rival paramilitary groups formed on both sides. Bombing, assassination and street violence formed a backdrop to life throughout the Troubles. In December 1971, 15 people, including two children, were killed when the Ulster Volunteer Force (UVF) bombed McGurk's Bar, the greatest loss of life in a single incident in Belfast. The Provisional IRA detonated 22 bombs within the confines of Belfast city centre on 21 July 1972, on what is known as Bloody Friday, killing nine people. Loyalist paramilitaries including the UVF and the Ulster Defence Association (UDA) said that the killings they carried out were in retaliation for the IRA campaign. Most of their victims were Catholics with no links to the Provisional IRA. A particularly notorious group, based on the Shankill Road in the mid-1970s, became known as the Shankill Butchers.

During the Troubles the Europa Hotel suffered 36 bomb attacks becoming known as "the most bombed hotel in the world". In all, over 1,600 people were killed in political violence in the city between 1969 and 2001.

21st century

Belfast city centre has undergone expansion and regeneration since the late 1990s, notably around Victoria Square. In late 2018, it was announced that Belfast would undergo a £500 million urban regeneration project known as "Tribeca" on a large city centre site. However, tensions and civil disturbances still occur despite the 1998 peace agreement, including sectarian riots and paramilitary attacks.

Belfast and the Causeway Coast were together named the best place to visit in 2018 by Lonely Planet. Tourist numbers have increased since the end of The Troubles, boosted in part by newer attractions such as Titanic Belfast and tours of locations used in the HBO television series Game of Thrones.