Thasos or Thassos (Greek: Θάσος, Thásos) is a Greek island, geographically part of the North Aegean Sea, but administratively part of the Kavala regional unit. It is the northernmost major Greek island, and 12th largest by area. Thassos is also the name of the largest town of the island (officially known as Limenas Thasou, “Port of Thasos”), situated at the northern side, opposite the mainland and about 10 kilometres (6 miles) from Keramoti. Thassos island is known from ancient times for its termae making it a climatic and balneoclimateric resort area.

Thasos’s economy relies on timber (it is rich in forests), marble quarries, olive oil and honey. Tourism has also become important since the 1960s, although not to the level of other Greek islands.