Drava or Drave (both: dräˈvə) [key], Ger. Drau, Hung. Dráva, river, c.450 mi (720 km) long, rising in the Carnic Alps, N Italy. It flows generally E through S Austria (where it is called the Drau) and enters Slovenia. It forms part of the Croatian-Hungarian border before joining the Danube River E of Osijek. The Mur River is its chief tributary. The lower course of the Drava is navigable.