A referendum was held in Northern Ireland on 22 May 1998 over whether there was support for the Good Friday Agreement.

A simultaneous referendum held in the Republic of Ireland produced an even larger majority (94.4%) in favour.

Republican Sinn Féin, which at the time did not run candidates in Northern Ireland, still opposes the agreement.

The referendum in the Republic of Ireland was held on the same day but rather than explicitly seeking approval of the Agreement itself it sought endorsement of constitutional amendments required by the Agreement, and produced an overwhelming Yes vote.

The turnout in Northern Ireland was noticeably high at 81.1% and also quite high evenly throughout Northern Ireland, compared to many elections where turnout is highest in strong nationalist areas and significantly lower in unionist areas.