The city stretches across 117 small islands in the marshy Venetian Lagoon along the Adriatic Sea in northeast Italy.

Situated on the Adriatic Sea, Venice always traded with the Byzantine Empire and the Muslim world extensively. By the late thirteenth century, Venice was the most prosperous city in all of Europe. At the peak of its power and wealth, it had 36,000 sailors operating 3,300 ships, dominating Mediterranean commerce.

The name is derived from the ancient Veneti people who inhabited the region by the 10th century B.C. The city historically was the capital of the Venetian Republic. Venice has been known as the "La Dominante", "Serenissima", "Queen of the Adriatic", "City of Water", "City of Masks", "City of Bridges", "The Floating City", and "City of Canals". Luigi Barzini described it in The New York Times as "undoubtedly the most beautiful city built by man". Venice has also been described as being one of Europe's most romantic cities.

The Republic of Venice was a major maritime power during the Middle Ages and Renaissance, and a staging area for the Crusades and the Battle of Lepanto, as well as a very important center of commerce (especially silk, grain, and spice) and art in the 13th century up to the end of the 17th century. This made Venice a wealthy city throughout most of its history. It is also known for its several important artistic movements, especially the Renaissance period. Venice has played an important role in the history of symphonic and operatic music, and it is the birthplace of Antonio Vivaldi.

While there are no historical records that deal directly with the obscure and peripheral origins of Venice, tradition and the available evidence have led several historians to agree that the original population of Venice consisted of refugees from Roman cities near Venice such as Padua, Aquileia, Treviso, Altino and Concordia (modern Portogruaro) and from the undefended countryside, who were fleeing successive waves of Germanic and Hun invasions. Some late Roman sources reveal the existence of fishermen on the islands in the original marshy lagoons. They were referred to as incolae lacunae ("lagoon dwellers"). The traditional founding is identified with the dedication of the first church, that of San Giacomo at the islet of Rialto (Rivoalto, "High Shore"), which is said to have been at the stroke of noon on 25 March 421.

Sometime in the first decades of the eighth century, the people of the lagoon elected their first leader Ursus, who was confirmed by Byzantium and given the titles of hypatus and dux. He was the first historical Doge of Venice.

During the reign of duke Agnello Particiaco (811–827) the ducal seat was moved from Malamocco to the highly protected Rialto, the current location of Venice. The monastery of St. Zachary and the first ducal palace and basilica of St. Mark, as well as a walled defense (civitatis murus) between Olivolo and Rialto were subsequently built here. Winged lions, which may be seen throughout Venice, are a symbol for St. Mark.

The city was governed by the Great Council, which was made up of members of the noble families of Venice. The Great Council appointed all public officials and elected a Senate of 200 to 300 individuals. Since this group was too large for efficient administration, a Council of Ten (also called the Ducal Council or the Signoria), controlled much of the administration of the city. One member of the great council was elected "Doge", or duke, the ceremonial head of the city, who normally held the title until his death.

The chief executive was the Doge, who theoretically held his elective office for life. In practice, several Doges were forced by pressure from their oligarchical peers to resign the office and retire into monastic seclusion when they were felt to have been discredited by perceived political failure. The Cavalieri di San Marco was the only order of chivalry ever instituted in Venice, and no citizen could accept or join a foreign order without the government's consent.