The Lostine River is a 31.4-mile-long (50.5 km) tributary of the Wallowa River in northeastern Oregon in the United States. It drains a portion of the Eagle Cap Wilderness of the Wallowa Mountains in the Wallowa–Whitman National Forest and joins the Wallowa River at Wallowa. In 1988, the upper 16 miles (26 km) of the Lostine River were listed as Wild and Scenic. A 5-mile (8 km) segment in the wilderness below the river's source at Minam Lake were classified "wild". The next 11 miles (18 km) were designated "recreational".