The Fonissa (Greek: Φόνισσα) is a stream in western Corinthia, Peloponnese, Greece.

It is 13.3 km (8.3 mi) long[1] and flows into the Gulf of Corinth.

The source of the river is in the hills near the village Rethi.

It flows a southeasterly direction through a narrow gorge, and empties into the Gulf of Corinth between the villages Kato Loutro and Kamari, 6 km northwest of Xylokastro.

This article related to a river in Greece is a stub.