Pionia (Ancient Greek: Πιονία) or Pioniai (Πιονίαι) was a town in the interior of ancient Mysia, on the river Satnioeis, to the northwest of Antandrus, and to the northeast of Gargara. Under the Roman dominion it belonged to the jurisdiction of Adramyttium, and in the ecclesiastical notices it appears as a bishopric of the Hellespontine province. The bishop Aetius represented the city at the Council of Ephesus. No longer the seat of a residential bishop, it remains a titular see of the Roman Catholic Church.
- Strabo. Geographica. Vol. xiii. p. 610. Page numbers refer to those of Isaac Casaubon's edition.
- Pliny. Naturalis Historia. Vol. 5.32.
- Hierocles. Synecdemus. Vol. p. 663.
- Catholic Hierarchy
- Richard Talbert, ed. (2000). Barrington Atlas of the Greek and Roman World. Princeton University Press. p. 56, and directory notes accompanying.
- Lund University. Digital Atlas of the Roman Empire.