Rathjen, variant Rathjens, is a surname. Notable people with the surname include:
Carl August Rathjens (1887–1966), German geographer Deborah Rathjen, Australian scientist Peter Rathjen (born 1964), Australian scientist and medical researcher Uwe Rathjen (born 1943), West German handball player Tobias Rathjen, German murderer; responsible for the Hanau shootings