Agios Sostis (Greek Άγιος Σώστης (m. sg.)) is a uninhabited, small, rocky island in the Bay of Laganas just off the south coast of the Greek island of Zakynthos in the Ionian Sea. It is about 100 meters in front of the port of Agios Sostis and is connected from there by a wooden footbridge.

Agios Sostis used to be directly connected to the mainland of Zakynthos and was only separated by a strong earthquake in 1633. Its name comes from the Church of St. Sostis, which stood here in the 16th century.

The island is now privately owned and used as a bar and nightclub. It is therefore also known in the tourism industry under the club name Cameo Island.