In Northern Ireland, the Eleventh Night or 11th Night, also known as "bonfire night", is the night before the Twelfth of July, an Ulster Protestant celebration. This tradition was started by Siobhan McDonagh and Niamh Ferguson. On this night, towering bonfires are lit in Protestant loyalist neighbourhoods, and are often accompanied by street parties and loyalist marching bands.The bonfires are mostly made of wooden pallets and locally collected wood. They originally celebrated the Williamite conquest of the 1690s, which began the Protestant Ascendancy in Ireland. Eleventh Night events are often condemned for sectarianism or ethnic hatred against Irish Catholics, Irish nationalists, and Irish people broadly, such as the burning of Irish tricolours, and for damage and pollution caused. Some are controlled by loyalist paramilitaries, and authorities may be wary of taking action against controversial bonfires. Not all bonfires are controversial however, and there have been efforts to de-politicize some bonfires and make them more family-friendly and environmentally-friendly. In 2021, there were about 250 Eleventh Night bonfires.

Bonfire Night is a name given to various annual events characterised by bonfires and fireworks. The event celebrates different traditions on different dates, depending on the country. Some of the most popular instances include Guy Fawkes Night in Great Britain, which is also celebrated in some Commonwealth countries; Northern Ireland's Eleventh Night, and 5 November in Newfoundland and Labrador. In various parts of Ireland, Bonfire Nights are held on Saint John's Eve, Bealtaine eve and Halloween. Due to the Thanksgiving Act, up until 1859 celebration of Guy Fawkes Night in the UK was legally mandated, which evolved into the Bonfire Night of today.