The Osam (Bulgarian: Осъм) is a river in north Bulgaria, with a length of 314 km an a catchment area of 2,820 km². The river takes its source from the foot of Levski Peak in Stara Planina, at an altitude of 1821 m. The Osam flows into the river Danube near the town of Nikopol. The ancient name of the river was Assamus.