Syros (Greek: Σύρος), or Siros or Syra is a greek island in the Cyclades, in the Aegean Sea. It is located 78 nautical miles (144 km) south-east of Athens. The island is home to the municipalities of Ermoupoli, Ano Syros, and Poseidonia. Ermoupoli is the capital of the island and the Cyclades. It has always been a significant port town, and during the 19th century it was even more significant than Piraeus.

During Roman times the capital of Syros was situated in the area of contemporary Ermoupoli. At the end of ancient times, the barbaric raids and piracy, which had surged the Aegean for many centuries, led Syros to decline. In the Byzantine years Syros constituted part of the Aegean Dominion, along with the rest of the Cycladic islands. After the overthrow of the Byzantium by the Venetians and Franks in 1204, Syros came under Venetian rule and was included in the Ducat of the Aegean. Meanwhile, Ano Syros was founded. During the Latin period, the majority of the local community were Roman Catholics, but maintained the greek language. During the reign of almost three and a half centuries of the Ducat of the Aegean, Syros had a singular feudal regime.

In the mid-16th century, the Ottoman fleet occupied the island and the Duchy fell apart. However, negotiations of the local authorities with the Ottomans gave the Cycladic islands substantial privileges, such as the reduction of taxes and religious freedom.

At the same time, following an agreement between France and the Vatican with the Ottoman authorities, the Catholics of the island came under the protection of France and Rome, a privilege maintained for centuries. After the second half of the 17th century, a period of economic recovery of the Aegean began, climaxing during the transition from the 18th to the 19th century. The special regime of the islands allowed the development of local self-government. The decline of piracy since the beginning of the 19th century led to the gradual liberation of the sea routes of the Eastern Mediterranean.

Due to its crucial geographical position, Syros became known as a maritime way-point. Moreover, the special social, religious and institutional conditions prevailing on the island led Syriots to neutrality at the beginning of the Greek Revolution in 1821. As a result, Syros became a secure shelter during the Revolution, attracting many Greek refugees from Asia Minor, Chios, Spetses, Psara, Aivali, Smyrna, Kydonia, Kassos and other places. Newcomers, mainly mariners and tradesmen, gave the island a new dynamic, which along with its demographic and economic development, turned it into an administrative and cultural centre.

Between 1822 and 1865, Ermoupoli was rebuilt in a Neoclassical style, merging Greek Classicism with elements of the Renaissance. Many landmarks such as the City Hall (designed by the famous German architect Ernst Ziller), the theatre Apollon by the Italian architect Campo (a miniature version of La Scala di Milano), the main Library, the General Hospital of Syros (Vardakeio-Proio), Miaoulis square and other buildings were built during that period of time.

Most public buildings, churches, schools, stadiums and many mansions were built in the same elegant and neoclassical style, making Ermoupoli at the time a very modern city with a unique character. As a result, Syros changed almost overnight from a rather quiet island into a vigorous centre of crafts, industry and production. Also, due to its large port of Ermoupoli, it turned into a major centre for ship building and refitting. Neorion was the first shipyard of Greece. To this very day, it remains a place where many ships are serviced and refitted.

Because of the Venetian domination from the Middle Ages and onwards, the islanders were exclusively Roman Catholic. However, due to immigration from other islands, Catholics now constitute some 47% of the population. The majority of the population are Greek Orthodox. They live peacefully side by side. Intermarriage between denominations is very common in Syros.

Beginning at the end of the 19th century and for several decades, a temporary economic recovery took place, due to the development of the textile industry. The Second World War reduced Syros' economic development, as was the case for every economic centre in Greece. However, already since the 80's, along with the generalized economic recovery and the rise of the living standards in Greece, elements of improvement appeared with tourism as its central axis. At the same time, the re-opening of the Neorion shipyards, as well as a number of other activities, indicate that Syros is on an upward trend. Ermoupoli today has 7 elementary schools, 4 gymnasiums (high schools), 2 technical schools and the Aegean University with a department of Fine Arts and system design, with a proposed future addition in Applied Arts and Visual Arts. The Syros Island National Airport, the Aegean casino, the frequent passenger boat transportation system and all other modern amenities help to attract many domestic and foreign tourists to the island all year round.