Maass or Maaß is a German surname. People with this surname include:
Clara Maass (1876–1901), American nurse
G. F. H. Maass (1830–1901), German botanist
Gustav Maass (1893–1964), American architect
Hans Maass (1911–1992), German mathematician
Hermann Maaß (1897-1944), resistance fighter
Johann Maass (1766–1823), German psychologist
Leberecht Maass (1863–1914), German admiral
Peter Maass (born 1960), American journalist