Sithonia, is a peninsula of Chalkidiki, which itself is located on a larger peninsula within Greece. The Kassandra Peninsula lies to the west of Sithonia and the Mount Athospeninsula to the east. Sithonia is also a municipality, covering the Sithonia peninsula. The seat of the municipality is the town Nikiti.

Geography
South, from the harbors exit there is Kartalia, the most southern part of Sithonia, a very impressive area which puts its visitors under a spell with its rocky secluded beaches. The beaches of Azapiko, Tristinika, Korakas, Marathias, Kalamitsi, and Kriaritsi are in the area. All the villages cover the peninsula mainly in the central and the southern portions. In the middle of Sithonia peninsula, near the village of Neos Marmaras, is the holiday resort of Porto Carras; the place of the 2003 European Union leaders Summit. The landscape is covered with vineyards, forests, grasslands, shrubland and mountains.

Municipality
The municipality Sithonia was formed at the 2011 local government reform by the merger of the following 2 former municipalities, that became municipal units.