Sithonia is a peninsula of the prefecture of Halkidiki and is the so-called middle peninsula of the prefecture's three. The peninsula of Sithonia is characterized by picturesque areas with strong relief and its organized or isolated beaches, as well as pine forests that characterize its landscape.

The peninsula is surrounded by the Sigitikos gulf to the east (today known as Mount Athos Gulf) and the Toroneos gulf to the west (today known as Kassandra Gulf). The mountain Itamos is located in the center of the peninsula. Among the many places in Sithonia are the ancient city, the castle and the church of Agios Athanasios in Toroni, the windmills in Sykia and the 16th century church in Nikiti. Nikiti is also the seat of the municipality of Sithonia. Porto Koufo is the largest bay and the most naturally safe harbor in Greece, mentioned by Thucydides. The largest settlement is Neos Marmaras, which is located in the middle of the peninsula and is the main commercial center of the area. There is also the large hotel unit of Porto Karras. At the heart of the peninsula is the area of Kartalia, where some of the most famous beaches are located, such as Azapiko, Tristinika, Korakas, Marathias, Kalamitsi, Kriaritsi, etc. On the other side we find the semi-mountainous settlement of Sykia with its beach, the touristic Sarti, Vourvourou and Ormos Panagias, located at the beginning of the peninsula.