Arnaut Guilhem (or Guillem) de Marsan (fl.
Arnaut was a member of the 1170 escort of Eleanor, daughter of Henry II of England, from Bordeaux to the Spanish border for her marriage to Alfonso VIII of Castile.
Arnaut Guilhem was also an Occitan lyric poet who composed one of the earliest ensenhamens or didactic poems: the Ensenhamen del cavalier (teaching of the cavalier).
The medievalist Mark Johnston notes that his work is similar to that of another 12th-century troubadour poet, Garin lo Brun.
According to an Occitan vida, the troubadour Peire de Valeira was from Arnaut Guilhem's lands.