Marius Flothuis, (30 October 1914 – 13 November 2001) born and died in Amsterdam, was a Dutch composer, musicologist and music critic.

His musicology studies continued at the University of Amsterdam under the direction of Albert Smijers and Karel Philippus Bernet Kempers [nl].

He was considered an authority in the field of Mozart music, which led him to write cadenzas for some of the composer's concertos.

Flothuis recognized his marked preference for French composers like Debussy and Ravel.

His music conveys rather subtle and concisely expressed universal values, attuned to a classical balance.