Syros (, ), also known as Siros or Syra, is a Greek island in the Cyclades, in the Aegean Sea. It is 78 nmi south-east of Athens. The area of the island is 83.6 km² 0 abbr=on and at the 2021 census it had 21,124 inhabitants.

The largest towns are Ermoupoli, Ano Syros, and . Ermoupoli is the capital of the island,