Diederik Maarten Samsom (born 10 July 1971) is a Dutch environmentalist and retired politician who was the leader of the Labour Party (Partij van de Arbeid, PvdA) from 2012 to 2016. He was the first leader in the 70-year history of the PvdA to have been voted out of his position by party members. He later served as head of cabinet for First Vice-President of the European Commission Frans Timmermans and his successor Wopke Hoekstra.