Theisoa (Ancient Greek: Θεισόα) was a town of ancient Arcadia, in the territory of Orchomenus. It is mentioned along with Methydrium and Teuthis as belonging to the confederation (συντέλεια) of Orchomenos.[1] Its inhabitants were removed to Megalopolis upon the foundation of the latter city (371 BCE).[1]
Its site is located near the modern Karkalous.[2][3]