Lenaert Jansz de Graeff (–) was a member of the family De Graeff and the son of Jan Pietersz Graeff, a rich cloth merchant from Amsterdam. Lenaert Jansz de Graeff was one of the leaders of the Protestant Reformation at Amsterdam, friend of Henry, Count of Bréderode, the "Grote Geus", and perhaps ident with "Monseigneur de Graeff", a captain of the Sea Beggars during the Capture of Brielle.