The Thessalian League (Thessalian Aeolic: Κοινὸν τοῦν Πετθαλοῦν, Koinòn toûn Petthaloûn; Attic: Κοινὸν τῶν Θετταλῶν, Koinòn tôn Thettalôn; Ionic and Koine Greek: Κοινὸν τῶν Θεσσαλῶν, Koinòn tôn Thessalôn) was a koinon or loose confederacy of feudal-like poleis and tribes in ancient Thessaly, located in the Thessalian plain in Greece. The seat of the Thessalian League was Larissa.