The Unac is a sinking river in Bosnia and Herzegovina. It rises beneath Šator mountain, flows through the municipality of Drvar, and finally meets Una River in Martin Brod. Also runs through two deep and rugged karstic canyons and it is dammed to form small Preodačko Lake and larger Župica Lake before it reaches the town of Drvar.
The lower course of the Unac River and its canyon is included in the Una National Park.
