Schlag is a German surname. Notable people with the surname include:
Evelyn Schlag (born 1952), Austrian poet and novelist Felix Schlag (1891–1974), United States currency designer Martha Schlag (1875–1956), German politician Pierre Schlag (born 1954), American legal writer Wilhelm Schlag (born 1969), American mathematician
See also Schlag bei Thalberg, a municipality in the district of Hartberg in Styria, Austria