Kato Koufonissi is a small island of the Cyclades located in the small Cyclades complex. has an area of 3,9 km². is uninhabited, and has only a few fishermen's homes, is inhabited mainly in the summer.
Kato Koufonissi has an area of 3.9 km² and belongs to the Small Cyclades, and to the Koufonisia Community. It is located south of Ano Koufonisi. Though previously there was a ten-family settlement, nowadays it is almost uninhabited, as it has only a few residences of fishermen and is mainly inhabited in the summer.