Maassen is a surname. Notable people with the surname include:
Frans Maassen (born 1965), Dutch cyclistFriedrich Maassen (1823–1900), German juristHanns Maaßen (1908–1983), German journalist and writerHans-Georg Maaßen (born 1962), German politician and lawyerNol Maassen (1922–2009), Dutch politicianPeter Maassen (1810–1890), German entomologistPeter J. Maassen, American juristSascha Maassen (born 1969), German racing driverTheo Maassen (born 1966), Dutch comedian and actorWolfgang Maassen, German philatelistXavier Maassen (born 1980), Dutch racing driver