Keizer is a Dutch surname, actually meaning "emperor" (related to German Kaiser). Notable people with the surname include:
Bert Keizer (born 1947), Dutch writer
Cees Keizer (born 1986), Dutch footballer
Garret Keizer, American author
Gerrit Keizer (1910-1980), Dutch sportsman
Jan Keizer (disambiguation), multiple people
Jan Keizer (referee) (born 1940), Dutch sports referee
Jan Keizer (singer) (born 1949), Dutch singer
Jolanda Keizer (born 1985), Dutch heptathlete
Joris Keizer (born 1979), Dutch swimmer
Martijn Keizer (born 1988), Dutch racing cyclist
Piet Keizer (born 1943), Dutch footballer
Sanne Keizer (born 1985), Dutch volleyball player
Simon Keizer (born 1984), Dutch singer