The Tucannon River is a tributary of the Snake River in the U.S. state of Washington. It flows generally northwest from headwaters in the Blue Mountains of southeastern Washington to meet the Snake 4 miles (6 km) upstream from Lyons Ferry Park and the mouth of the Palouse River. The Tucannon is about 62 miles (100 km) long. Part of the upper river flows through the Wenaha–Tucannon Wilderness.