Lassen is a Danish patronymic surname meaning "son of Lars" (equivalent of Laurentius), and thus a parallel form of the more common surname Larsen. Notable people with the surname include:
Anders Lassen (1920-1945), a Danish recipient of the British Victoria Cross
Christian Lassen, a Norwegian-German orientalist
Clyde Everett Lassen, a United States Navy aviator and Medal of Honor recipient
Eduard Lassen, a Belgian composer
Erik Sætter-Lassen (1892–1966), a Danish sport shooter
Frederik Lassen, a Danish football player
Georg Lassen, a German former U-boat captain
Hans Christian Lassen, a Danish sprint canoer
Hartvig Lassen (1824–1897), a Norwegian editor and literary historian
Henrik Andreas Zetlitz Lassen, a Norwegian politician
Inger Lassen (1911–1957), a Danish film actress
Jean Elisabeth Lassen, a Canadian weightlifter
Justin Lassen, an American composer, producer, multi-instrumentalist and remixer
Leigh Lassen, an American actress
Leo Lassen (1899–1975),an American baseball announcer
Niels A. Lassen (1926-1997), a Danish medical researcher
Peter Lassen, a Danish-American rancher, prospector and explorer
Peter Lassen (footballer), a Danish former football striker
Werner Lassen, a Namibian amateur golfer
Lassen may also refer to Lassen Peak, located in Lassen Volcanic National Park, a national park in the United States.
