亚得里亚海（意大利语：Mar Adriatico，斯洛文尼亚语：Jadransko morje，克罗地亚语：Jadransko more，阿尔巴尼亚语：Deti Adriatik），是地中海的一部分水域，分隔了意大利半岛（亚平宁半岛）和巴尔干半岛，也分隔了亚平宁山脉与狄那里克阿尔卑斯山脉及其临近地区。亚得里亚海西岸属于意大利，东岸则分别属于斯洛文尼亚、克罗地亚、波斯尼亚和黑塞哥维那、黑山和阿尔巴尼亚。亚得里亚海透过位于其南部的奥特朗托海峡与爱奥尼亚海相连。波河、阿迪杰河、奥凡托河等河流流入亚得里亚海；海中有近1200个岛屿，其中只有69个有人居住。 

Das Adriatische Meer, kurz auch die Adria (lateinisch Mare Adriaticum; italienisch Mare Adriatico; bosnisch, kroatisch und serbisch Jadransko more oder kurz Jadran; slowenisch Jadransko morje; albanisch Deti Adriatik oder kurz Adriatiku), ist das lang gestreckte nördliche Seitenbecken des Mittelmeeres zwischen der Apenninhalbinsel und Balkanhalbinsel. Es ist nach der Stadt Adria in Italien (Provinz Rovigo) benannt. Zum Adriatischen Meer wird alles gerechnet, was nördlich der Straße von Otranto liegt.

アドリア海（アドリアかい、英: Adriatic Sea ; イタリア語: Mar Adriatico ; クロアチア語: Jadransko more）は、地中海の海域の一つ。イタリア半島とバルカン半島に挟まれている。 

The Adriatic Sea (/ˌeɪdriˈætɪk/) is a body of water separating the Italian Peninsula from the Balkans. 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 over 1,300 islands, mostly located along the Croatian part of 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 1,233 metres (4,045 ft). The Otranto Sill, an underwater ridge, is located at the border between the Adriatic and Ionian Seas. The prevailing currents flow counterclockwise from the Strait of Otranto, along the eastern coast and back to the strait along the western (Italian) coast. Tidal movements in the Adriatic are slight, although larger amplitudes are known to occur occasionally. The Adriatic's salinity is lower than the Mediterranean's because the Adriatic collects a third of the fresh water flowing into the Mediterranean, acting as a dilution basin. The surface water temperatures generally range from 30 °C (86 °F) in summer to 12 °C (54 °F) in winter, significantly moderating the Adriatic Basin's climate.

The Adriatic Sea sits on the Apulian or Adriatic Microplate, which separated from the African Plate in the Mesozoic era. The plate's movement contributed to the formation of the surrounding mountain chains and Apennine tectonic uplift after its collision with the Eurasian plate. In the Late Oligocene, the Apennine Peninsula first formed, separating the Adriatic Basin from the rest of the Mediterranean. All types of sediment are found in the Adriatic, with the bulk of the material transported by the Po and other rivers on the western coast. 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 karst habitats and biodiversity. The sea is abundant in flora and fauna—more 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. The earliest settlements on the Adriatic shores were Etruscan, Illyrian, and Greek. By the 2nd century BC, the shores were under Rome's control. In the Middle Ages, the Adriatic shores and the sea itself were controlled, to a varying extent, by a series of states—most notably the Byzantine Empire, the Croatian Kingdom, the Republic of Venice, the Habsburg Monarchy and the Ottoman Empire. The Napoleonic Wars resulted in the First French Empire gaining coastal control and the British effort to counter the French in the area, ultimately securing most of the eastern Adriatic shore and the Po Valley for Austria. Following Italian unification, the Kingdom of Italy started an eastward expansion that lasted until the 20th century. Following World War I and the collapse of Austria-Hungary and the Ottoman Empire, the eastern coast's control passed to Yugoslavia and Albania. The former disintegrated during the 1990s, resulting in four new states on the Adriatic coast. Italy and Yugoslavia agreed on their maritime boundaries by 1975 and this boundary is recognised by Yugoslavia's successor states, but the maritime boundaries between Slovenia, Croatia, Bosnia-Herzegovina, and Montenegro are still disputed. Italy and Albania agreed on their maritime boundary in 1992.

Fisheries and tourism are significant sources of income all along the Adriatic coast. Adriatic Croatia's tourism industry has grown faster economically than the rest of the Adriatic Basin's. Maritime transport is also a significant branch of the area's economy—there 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 Adriatic seaport by passengers served per year.

La mer Adriatique (du latin : Mare Hadriaticum ou Mare Adriaticum) est une mer séparant la péninsule italienne de la péninsule balkanique. L'Adriatique est le bras de la Méditerranée situé le plus au nord en s'étendant du canal d'Otrante (où elle rejoint la mer Ionienne) jusqu'aux villes de Venise et de Trieste et à l'embouchure du Pô. Les pays côtiers sont l'Italie, la Slovénie, la Croatie, la Bosnie-Herzégovine, le Monténégro et l'Albanie, ainsi que la Grèce par l'île de Corfou. 

Il mare Adriatico è l'articolazione del mar Mediterraneo orientale situata tra la penisola italiana e la penisola balcanica; suddiviso in Alto Adriatico, Medio Adriatico e Basso Adriatico, bagna sei Paesi: Italia, Slovenia, Croazia, Bosnia ed Erzegovina, Montenegro e Albania, confinando a sud-est con il Mar Ionio. 

El mar Adriático (del latín, Mare Hadriaticum) es un golfo estrecho y alargado que forma parte del mar Mediterráneo. Se encuentra situado entre la península Itálica, al oeste, y la península de los Balcanes, al este, con una anchura máxima de unos 200 km, y una longitud de unos 800 km. Su extremo meridional limita con el mar Jónico, del que lo separa el canal de Otranto. Su superficie total es de, aproximadamente, 160 000 km².

Las costas occidental, septentrional, y parte de la oriental corresponden a Italia (60% de la longitud de costa del Adriático), mientras que el resto de la costa oriental corresponde a Croacia, Eslovenia, Bosnia y Herzegovina, Montenegro y Albania. Algunos de los ríos que desembocan en el Adriático son el Reno, el Po, el Adigio, el Brenta, el Piave y el Neretva.

La costa del Adriático concentra un gran número de centros turísticos, como Venecia, que recibe el nombre de «Reina del Adriático». Tras la división de Yugoslavia, la costa croata se ha convertido también en un destino turístico muy popular.

Sus aguas sostienen industria pesquera, y se llevan a cabo prospecciones petrolíferas en este mar. Durante los años 1990, varias investigaciones revelaron que sus niveles de contaminación son muy altos.

En las últimas décadas el gobierno de Italia ha intentado hacer de él una barrera contra la inmigración ilegal, en su mayor parte proveniente de Albania.

Адриати́ческое мо́ре (итал. mare Adriatico, эмил.-ром. Mèr Adriâtic, вен. Mar Adriàtico, неап. Mar Adriateco, словен. Jadransko morje, сербохорв. Jadransko more/Јадранско море, алб. Deti Adriatik, лат. mare Hadriaticum), также Адриатика — полузамкнутое море, часть Средиземного моря между Апеннинским и Балканским полуостровами. Омывает берега Италии (более 1000 км), Словении (47 км), Хорватии (1777 км), Боснии и Герцеговины (20 км), Черногории (200 км), Албании (472 км).