Mysia (/ˈmɪʒə/ or /ˈmiːʒə/; Greek: Μυσία, Latin: Mysia) was a region in the northwest of ancient Asia Minor or Anatolia (part of modern Turkey). It was located on the south coast of the Sea of Marmara. It was bounded by Bithynia on the east, Phrygia on the southeast, Lydia on the south, Aeolis on the southwest, Troad on the west and by the Propontis on the north. In ancient times it was inhabited by the Mysians, Phrygians, Aeolian Greeks, and other groups.
The precise limits of Mysia are difficult to assign. The Phrygian frontier was fluctuating, while in the northwest the Troad was only sometimes included in Mysia. The northern portion was known as Lesser Phrygia or Phrygia Minor (Ancient Greek: μικρὰ Φρυγία), while the southern was called Major or Pergamene. Mysia was in later times also known as Phrygia Hellespontica (Ἑλλησποντιακὴ Φρυγία, "Hellespontine Phrygia") or Phrygia Epictetus (ἐπίκτητος Φρυγία, "acquired Phrygia"), so named by the Attalids when they annexed the region to the Kingdom of Pergamon.