Theodor Becker (23 June 1840 in Plön – 30 June 1928 in Liegnitz) was a Danish-born German civil engineer and entomologist primarily known for studies on the taxonomy of flies. He worked with Paul Stein, Mario Bezzi, and Kálmán Kertész on Katalog der Paläarktischen dipteren published in Budapest from 1903.