Frederik Theodor Kloss was a German-Danish painter who specialized in marine painting.

Kloss attended the Berlin Academy where he studied under Carl Schumann (1767-1827). He travelled to Prague, Breslau and Dresden (1825–27), North Sea (1832), Iceland (1834), the Mediterranean Sea (1843) and the Faroe Islands (1844). On seeing one of Christoffer Wilhelm Eckersberg's marine paintings in Dresden, Kloss decided to go to Copenhagen and become one of his students at the Danish Academy. Over the years, the two became great friends not only in art but also as members of the Free Masons. Kloss became fully integrated into Danish cultural life. After becoming a member of the Academy in 1840, he received a professorship in 1853 and was treasurer from 1867.