The Venetian Lagoon is an enclosed bay of the Adriatic Sea, in northern Italy, in which the city of Venice is situated. Its name in the Italian and Venetian languages, Laguna Veneta (cognate of Latin lacus ‘lake‘), has provided the English name for an enclosed, shallow embayment of salt water: a lagoon.

The Venetian Lagoon stretches from the River Sile in the north, to the Brenta in the south, with a surface area of around 550 square kilometres (212 square miles). It is around 8% land, including Venice itself and many smaller islands. About 11% is permanently covered by open water, or canals, as the network of dredged channels are called, while around 80% consists of mud flats, tidal shallows and salt marshes. The Lagoon is the largest wetland in the Mediterranean Basin.

It is connected to the Adriatic Sea by three inlets: Lido, Malamocco and Chioggia. Situated at one end of a largely enclosed sea, the lagoon is subject to large variations in its water level. The most extreme are the spring tides known as the acqua alta (Italian for “high water”), which regularly flood much of Venice.

The nearby Marano-Grado Lagoon, with a surface area of around 160 square kilometres (62 square miles), is the northernmost lagoon in the Adriatic Sea and is sometimes called the “twin sister of the Venetian Lagoon”.