Agios Konstantinos is a village in Kalamata Municipality, in the regional unit of Messenia, in the region of Peloponnese, Greece. Agios Konstantinos lies 0.1 km from the Taygetus mountains. It has 158 inhabitants (2021). The nearest city is Kalamata, 15.0 km to the southeast. Among the landmarks around are Messene (12.2 km), Mystras (32 km) and Temple of Apollo at Bassae (32 km). Among the natural features are Cave of Caiada (29 km).
Also written Άγιος Κωνσταντίνος.