Stymfalia is a village and a former municipality in Corinthia, Peloponnese, Greece. Since the 2011 local government reform, it has formed part of the municipality of Sikyona, of which it is a municipal unit. The municipal unit has an area of 205.07 km2, while its population as of 2021 was 1,898. The seat of the municipality was in Kalianoi, 41 km southwest of the town of Kiato. The municipal unit occupies a mountain valley with an average altitude of 600 metres. Mount Kyllene dominates it to the NW, rising to a height of c. 2,400 metres. The largest village is Kaisari, but the principal antiquities are just south of the modern village of Stymfalia, a hamlet of about 150 inhabitants.