John Martin McDonnell (born 8 September 1951) is a British politician who has served as the Member of Parliament (MP) for Hayes and Harlington since 1997. A member of the Labour Party, he was Shadow Chancellor of the Exchequer from 2015 to 2020. McDonnell was suspended from the parliamentary party in July 2024, and sat as an independent until the Chief Whip restored his membership in September 2025.