Danish painter and graphic artist. A 1977 graduate of the Funen Academy of Fine Arts, he studied with Dan Sterup-Hansen at the Royal Danish Academy of Fine Arts from 1982 to 1984.

Stylistically, he belongs to the neo-realism movement, and often uses photographs as a starting point for the creation of his paintings.

Peter Martensen has portrayed former Folketing presidents Erling Olsen and Christian Mejdahl. The portraits hang in the Folketing. Other works have been exhibited at Kastrupgårdsamlingen, Statens Museum for Kunst, Vejle Kunstmuseum and London's Victoria and Albert Museum.