Serifos is a Greek island municipality in the Aegean Sea, located in the western Cyclades, south of Kythnos and northwest of Sifnos. It is part of the Milos regional unit. The area is 75.207 square kilometres (29.038 sq mi) and the population was 1,420 at the 2011 census. It is located about 170 kilometres ESE of the Athenian port of Piraeus.