DeMars (and variants) is a surname. Notable people with the surname include:
AnnMaria De Mars (born 1958), American technology executive, author and JudokaBilly DeMars (born 1925), American baseball shortstop and coachBruce DeMars (born 1935), United States Navy four star admiralHélène-Louise Demars (born c. 1736), French composerLina Van de Mars (born 1979), German TV moderator, motor athlete and drummerNicole Demars (born 1970), Canadian road cyclistVernon DeMars (1908-2005), American architect and professor