Sifnos (Greek: Σίφνος) is an islan municipality in the Cyclades island group in Greece. The main town on the island is known as Apollonia (pop. 942) located near the center of the island. The second-largest town is Artemon (744). Another major population center is the hilltop village named Kastro (101), built on top of a high cliff on its northwestern shore. The port settlement, on the west cost of the island is known as Kamares (188).