The Northern Ireland Assembly (Irish: Tionól Thuaisceart Éireann, Ulster Scots: Norlin Airlann Semmlie ) is the devolved legislature of Northern Ireland. It has power to legislate in a wide range of areas that are not explicitly reserved to the Parliament of the United Kingdom, and to appoint the Northern Ireland Executive. It sits at Parliament Buildings at Stormont in Belfast.

The latest incarnation of the Assembly was established under the terms of the Good Friday Agreement of 1998, an accord aimed at bringing an end to Northern Ireland's violent 30-year Troubles. It is based on the principle of power-sharing under the D'Hondt method, in order to ensure that the largest political communities in Northern Ireland, unionist and nationalist, participate in governing the region. The Assembly is a unicameral, democratically elected body comprising 108 members who are known as Members of the Legislative Assembly, or MLAs. Members are elected under the single transferable vote form of proportional representation.

The Assembly has been suspended on multiple occasions throughout its history, the longest being from 14 October 2002 until 7 May 2007, a period of over four and a half years; during these suspensions, its powers reverted to the Northern Ireland Office. Following talks that resulted in the St Andrews Agreement being accepted in November 2006, an election to the Assembly was held on 7 March 2007 and full power was restored to the devolved institutions on 8 May 2007.