Agios Konstantinos is a village in Aigialeia Municipality, in the regional unit of Achaea, in the region of West Greece, Greece. Agios Konstantinos lies 0.1 km from the Panachaiko mountains. It has 407 inhabitants (2021). The nearest city is Patras, 27 km to the west. Beaches nearby: Akoli (1.8 km), Akoli (2 km), Alyki (4.9 km). Among the landmarks around are Helike (9.4 km), Apollon Theatre (28 km) and Mega Spilaio (22 km). Among the natural features are Cave of the Lakes (34 km) and cave of the oracle of Heracles Vouraikos (13.5 km).

Also written Άγιος Κωνσταντίνος.