The Battle of Halmyros, known by earlier scholars as the Battle of the Cephissus or Battle of Orchomenos, was fought on 15 March 1311, between the forces of the Frankish Duchy of Athens and its vassals under Walter of Brienne against the mercenaries of the Catalan Company, resulting in a decisive victory for the mercenaries.

The Frankokratia, also known as Latinokratia and, for the Venetian domains, Venetokratia or Enetokratia, was the period in Greek history after the Fourth Crusade (1204), when a number of primarily French and Italian states were established by the Partitio terrarum imperii Romaniae on the territory of the dissolved Byzantine Empire.