Klassen is a surname. Notable people with the surname include:
Ben Klassen (1918–1993), American white supremacist and founder of the religion Creativity
Cindy Klassen (born 1979), Canadian skater
Danny Klassen (born 1975), American-Canadian baseball player
Johann Peter Klassen (1889–1947), German-Canadian poet
Kenneth Klassen (born 1951), Canadian sex tourist
Kim Klassen (born 1968), American folk art painter
Linda Klassen, Canadian politician
Peter P. Klassen (born 1926), Paraguayan Mennonite historian
Sarah Klassen (born 1932), Canadian poet
Terry Klassen, Canadian voice actor and voice director