The Adriatic Sea ( /ˌeɪdriˈætɨk/) is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges. The Adriatic Sea is a northwest-to-southeast arm of the Mediterranean Sea.

The western coast is Italian, while the eastern coast runs along Slovenia (47 km), Croatia (5,835 km) , Bosnia and Herzegovina (26 km), Montenegro (294 km), and Albania (295 km). Major rivers joining the Adriatic are the Reno, Po, Adige/Etsch, Brenta, Piave, Soča/Isonzo, Zrmanja, Krka, Cetina, Neretva, and Drin (Drini).