Stephen Ronald Aiken OBE MLA (born 16 June 1962) is a Northern Irish politician, who served as Leader of the Ulster Unionist Party (UUP) from 2019 to 2021, and was Chief Whip of the UUP from 2017 to 2019. Aiken has been a Member of the Northern Ireland Assembly (MLA) for South Antrim since 2016.