The Cyclades comprise about 220 islands, the major ones being Amorgos, Anafi, Andros, Antiparos, Delos, Ios, Kea, Kimolos, Kythnos, Milos, Mykonos, Naxos, Paros, Folegandros, Serifos, Sifnos, Sikinos, Syros, Tinos, and Thira or Santoríni. There are also many minor islands including Donousa, Eschati, Gyaros, Irakleia, Koufonisia, Makronisos, Rineia, and Schoinousa.

The name "Cyclades" refers to the islands forming a circle ("circular islands") around the sacred island of Delos. Most of the smaller islands are uninhabited. Ermoupoli on Syros is the chief town and administrative center of the former prefecture. The islands are peaks of a submerged mountainous terrain, with the exception of two volcanic islands, Milos and Santorini.

The climate is generally dry and mild, but with the exception of Naxos the soil is not very fertile; agricultural produce includes wine, fruit, wheat, olive oil, and tobacco. Cooler temperatures are in higher elevations and mainly do not receive wintry weather.