Jonathan Lansman (born 9 July 1957) is a British political activist. He is best known for having worked on Jeremy Corbyn's successful 2015 campaign for the leadership of the Labour Party and subsequently founded the pro-Corbyn organisation Momentum. He is a member of the Labour Party's National Executive Committee. Lansman has worked for both Tony Benn and Michael Meacher, and was a prominent supporter of Benn in the early 1980s.