The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to the northwest and the Po Valley. The countries with coasts on the Adriatic are Albania, Bosnia and Herzegovina, Croatia, Italy, Montenegro, and Slovenia.
The Adriatic contains more than 1,300 islands, mostly located along its eastern coast. It is divided into three basins, the northern being the shallowest and the southern being the deepest, with a maximum depth of . The prevailing currents flow counterclockwise from the Strait of Otranto. Tidal movements in the Adriatic are slight, although larger amplitudes occur occasionally. The Adriatic's salinity is lower than the Mediterranean's because it collects a third of the fresh water flowing into the Mediterranean, acting as a dilution basin. The surface water temperatures generally range from in summer to in winter, significantly moderating the Adriatic Basin's climate. The Adriatic Sea sits on the Apulian or Adriatic Microplate. In the Late Oligocene, the Italian Peninsula first formed, separating the Adriatic Basin from the rest of the Mediterranean. The western coast is alluvial or terraced, while the eastern coast is highly indented with pronounced karstification. There are dozens of marine protected areas in the Adriatic, designed to protect the sea's habitats and biodiversityâÂÂmore than 7,000 species are identified as native to the Adriatic, many of them endemic, rare and threatened ones.
The Adriatic's shores are populated by more than 3.5 million people; the largest cities are Bari, Venice, Trieste and Split. Early settlements on the Adriatic shores were Etruscan, Illyrian, and Greek. By the 2nd century BC, the region was under Rome's control. In the Middle Ages, the sea was controlled, to a varying extent, by a series of statesâÂÂmost notably the Byzantine Empire, the Croatian Kingdom, the Republic of Venice, the Habsburg monarchy and the Ottoman Empire. The Napoleonic Wars resulted in the Austrian Empire gaining control of most of the eastern Adriatic shore and the Po Valley, while the Kingdom of Italy gradually took control of the remaining Italian coast during the 19th century. Following the collapse of Austria-Hungary in 1918, control of the eastern coast passed to Yugoslavia and Albania, which agreed on their maritime boundaries with Italy in 1975 and 1992 respectively. After Yugoslavia's dissolution during the 1990s, its four coastal successor statesâÂÂSlovenia, Croatia, Bosnia and Herzegovina, and MontenegroâÂÂcontinued to recognise the previous maritime border with Italy, but have disputed the borders between themselves.
Fisheries and tourism are significant sources of income along the Adriatic coast. Maritime transport is also a significant branch of the area's economyâÂÂthere are 19 seaports in the Adriatic that each handle more than a million tonnes of cargo per year. The largest Adriatic seaport by annual cargo turnover is the Port of Trieste, while the Port of Split is the largest by passengers served per year.
The origins of the name Adriatic are linked to the Etruscan settlement of Adria, which probably derives its name from Illyrian adur 'water, sea'. In classical antiquity, the sea was known as Mare Adriaticum (Mare Hadriaticum, also sometimes simplified to Adria) or, less frequently, as Mare Superum '[the] upper sea'. The two terms were not synonymous, however. Mare Adriaticum generally corresponds to the Adriatic Sea's extent, spanning from the Gulf of Venice to the Strait of Otranto. That boundary became more consistently defined by Roman authorsearly Greek sources place the boundary between the Adriatic and Ionian seas at various places ranging from adjacent to the Gulf of Venice to the southern tip of the Peloponnese, eastern shores of Sicily and western shores of Crete. Mare Superum on the other hand normally encompassed both the modern Adriatic Sea and the sea off the Apennine peninsula's southern coast, as far as the Strait of Sicily. Another name used in the period was Mare Dalmaticum, applied to waters off the coast of Dalmatia or Illyricum. During the early modern period, the entire sea was also known as the Gulf of Venice (), although that name is now informally applied only to the northern area of the sea, from Maestra Point in the Po Delta to Cape Kamenjak on the Istrian Peninsula.
The names for the sea in the languages of the surrounding countries include ; ; ; ; ; ; , ÃÂðôÃÂðýÃÂúþ üþÃÂõ; ; . In Serbo-Croatian and Slovene, the sea is often referred to as simply Jadran.
The Adriatic Sea is a semi-enclosed sea, bordered in the southwest by the Apennine or Italian Peninsula, in the northwest by the Italian regions of Veneto and Friuli-Venezia Giulia, and in the northeast by Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, and AlbaniaâÂÂthe Balkan peninsula. In the southeast, the Adriatic Sea connects to the Ionian Sea at the wide Strait of Otranto. The International Hydrographic Organization (IHO) defines the boundary between the Adriatic and the Ionian seas as a line running from the Butrinto River's mouth (latitude 39ð44'N) in Albania to the Karagol Cape in Corfu, through this island to the Kephali Cape (these two capes are in latitude 39ð45'N), and on to the Santa Maria di Leuca Cape (latitude 39ð48'N). It extends from the northwest to the southeast and is wide. It covers and has a volume of . The Adriatic extends northwest from 40ð to 45ð47' north, representing the Mediterranean's northernmost portion. The sea is geographically divided into the Northern Adriatic, Central (or Middle) Adriatic, and Southern Adriatic.
The Adriatic Sea drainage basin encompasses , yielding a landâÂÂsea ratio of 1.8. The drainage basin's mean elevation is above sea level, with a mean slope of 12.1ð. Major rivers discharging into the Adriatic include the Po, SoÃÂa, Krka, Neretva, Drin, Buna, and Vjosë. In the late 19th century, Austria-Hungary established a geodetic network with an elevation benchmark using the average Adriatic Sea level at the Sartorio pier in Trieste, Italy. The benchmark was subsequently retained by Austria, adopted by Yugoslavia, and retained by the states that emerged after its dissolution. In 2016, Slovenia adopted a new elevation benchmark referring to the upgraded tide gauge station in the coastal town of Koper.
The Alps, which also have a large meteorological impact on the Mediterranean, touch the Adriatic in the area around Trieste towards Duino and Barcola.