Horstmann is a surname. Notable people with the surname include:
August Friedrich Horstmann (1842–1929), German physical chemist
Carl Horstmann, 19th-century editor of The Early South-English Legendary
Cay Horstmann, author of several computer programming books and the creator of the Horstmann indent style Dennis Horstmann (born 1980), German DJ and dance music artist known as 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 Karl Horstmann (born 1967), American film director, writer and producer Ken Horstmann (born 1971), American film and television director 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