Arnaut Guilhem (or Guillem) de Marsan (fl. 1160–1180) was a Landais nobleman and troubadour. He was descended from a cadet branch of the viscounts of Marsan and was himself lord of Roquefort and Montgaillard and co-lord of Marsan. 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. He is attested in a charter of Eleanor of Aquitaine.