Moritz Werner Fenchel (German: [ˈfɛnçəl]; 3 May 1905 – 24 January 1988) was a German-Danish mathematician known for his contributions to geometry and to optimization theory.

A German-born Jew and early refugee from Nazi suppression of intellectuals, Fenchel lived most of his life in Denmark.

[1] He wrote his doctorate thesis in geometry (Über Krümmung und Windung geschlossener Raumkurven)[2] under Ludwig Bieberbach.

During a one-year leave (on Rockefeller Fellowship) between 1930 and 1931, Fenchel spent time in Rome with Levi-Civita, as well as in Copenhagen with Harald Bohr and Tommy Bonnesen.

[3] Fenchel emigrated to Denmark somewhere between April and September 1933, ultimately obtaining a position at the University of Copenhagen.