Syros, also known as Siros or Syra, is a Greek island in the Cyclades, in the Aegean Sea. It is 78 nautical miles (144 km) south-east of Athens. The area of the island is 83.6 km2 (32 sq mi) and at the 2021 census it had 21,124 inhabitants.

The Cyclades are an island group in the Aegean Sea, southeast of mainland Greece and a former administrative prefecture of Greece. They are one of the island groups which constitute the Aegean archipelago. The name refers to the archipelago forming a circle around the sacred island of Delos. The largest island of the Cyclades is Naxos, however the most populated is Syros.