Sir Jeffrey Mark Donaldson (born 7 December 1962) is a Northern Irish politician. He was the leader of the Democratic Unionist Party (DUP) from 2021 to 2024 and the leader in the UK House of Commons from 2019 to 2024. He has been the Member of Parliament (MP) for Lagan Valley since 1997. He is Northern Ireland's longest-serving current MP.