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
Heinrich Klassen (born 1991), South African cricketer
Danny Klassen (born 1975), American-Canadian baseball player
Eduard Klassen, Paraguayan harpist
Ernie Klassen, Canadian politician
George Klassen (born 2002), American baseball player
Johann Peter Klassen (1889–1947), German-Canadian poet
Jon Klassen (born 1981), Canadian writer and illustrator of children's books
Kenneth Klassen (born 1951), Canadian sex tourist
Linda Klassen, Canadian politician
Owen Klassen (born 1991), Canadian basketball player
Peter P. Klassen (1926–2018), Paraguayan Mennonite historian
Sarah Klassen (born 1932), Canadian poet
Terry Klassen, Canadian voice actor and voice director