Horstmann is a surname. Notable people with the surname include:
Carl Horstmann, editor of the Middle English South English Legendary
Cay Horstmann, the author of several computer programming books and the creator of the Horstmann indent style
Dennis Horstmann, see Special D.
Dorothy M. Horstmann (1911–2001), American epidemiologist, virologist and pediatrician
Ignatius Frederick Horstmann (1840–1908), American Roman Catholic bishop
Kai Horstmann (born 1981), English rugby union player
Ken Horstmann (born 1971), American actor
Oscar Horstmann (1891–1977), American baseball player
Roy Horstmann (1910–1998), American football player
Sidney Horstmann (1881–1962), British automotive engineer and businessman
Ulrich Horstmann (born 1949), German literary scholar and writer
