Beaches from A - F

Agathopes. Close to Delagrazzia (Poseidonia), a sandy cosmopolitan and organized beach. Water sports are available, along with beach bars. Komito beach is nearby.
Achladi. A small cove, next to Vari beach, at the southern coast. It is organized and shady.
Ampela: A sandy/pebbly beach located at the southern coast of the island.
Armeos (Agia Pakou): Secluded beach near Galissas, beneath Ayia Pakou hill. It is preferred by naturists.
. On the eastern coast of Syros, a pebbly beach with shallow waters, suitable for families.
Delagrazzia (Poseidonia). The beach of the homonymous beautiful settlement. Small and cosmopolitan, with pebbles.
Delfini. This sandy, popular beach was awarded a Blue Flag. There are taverns and beach bars.
In Ermoupolis. There is a beach bar beneath St. Nikolas in the Vaporia district.
Fabrica. Small, peaceful, sandy/pebbly beach, next to Vari, featuring a yacht port. It is at the southern coast, ideal for windsurfing. 
Finikas. An extended beach in the homonymous settlement. It is lined up with beach-bars and taverns, featuring also a marina.

Beaches from G - V

Galissas. An extended, popular, organized beach with all-day restaurants and bars, rooms to rent, small shops and many more.
Kini. The beautiful cove near Captain’s Hotel. Picturesque, popular, sandy, and organized. It features beach-bars and all-day restaurants/taverns. There are mini markets and a small fishing harbor.

Kokkina. Pebbly beach, very close to Finikas, with all-day cafes and small shops.
Komito: Sandy/pebbly sheltered beach, near Agathopes.  
Lotos. Small, sandy beach very close to Kini.
Megas Gialos. Extended, organized, pebbly and shady beach, comprised of small coves. There are canoes and water bikes to rent.
Santorinioi: 1.5 km away from the central road leading to Vari, ideal for windsurfing.
Vari. Organized beach, preferred by yacht owners.

Northwest beaches

They are very beautiful but accessible only by boat or hiking: Varvaroussa, Aetos, Lia, Grammata, Megas Lakos, Marmari, Avlaki.