Matthew Blastares (Greek: Ματθαῖος Βλαστάρης or Βλάσταρις, romanized: Matthaios Blastares/Blastaris; fl. 1335–1346) was a 14th-century Byzantine Greek monk in Thessalonica and early scholarly opponent of reconciliation with Rome. He was also the writer of the Syntagma Canonum.