Wenaha–Tucannon Wilderness, Nature reserve in Asotin County, United States.

Wenaha–Tucannon Wilderness is a federally designated wilderness of 177,423 acres in the Blue Mountains of northeastern Oregon and southeastern Washington, managed within Umatilla National Forest. It consists mainly of basaltic ridges cut by deep canyons with steep slopes, drained by the Wenaha, Tucannon, Grande Ronde and Asotin rivers. Elevations run from 2,000 feet on the Wenaha River to 6,401 feet atop Oregon Butte in Washington.

The Wenaha–Tucannon Wilderness was created by the Endangered American Wilderness Act of 1978, which set aside 177,423 acres in the Umatilla National Forest: 66,375 acres in Oregon and 111,048 acres in Washington. The U.S. Forest Service manages the area.

The wilderness lies in the Blue Mountains homeland of the Cayuse, Umatilla and Walla Walla peoples, whose descendants are today the Confederated Tribes of the Umatilla Indian Reservation. The area is managed by the Umatilla National Forest, and tribal hunting and fishing rights in the ceded lands remain in force.

Multiple trailheads like Three Forks, Godman, and Troy provide access to about 200 miles of hiking routes throughout the area. Summer is the best time to visit, as snow melts and trails become easily passable.

The wilderness is split between two states: 111,048 acres lie in Washington and 66,375 acres in Oregon, all within Umatilla National Forest. Its lowest point is the Wild and Scenic Wenaha River at 2,000 feet; Oregon Butte, at 6,401 feet, is the highest summit in Washington's Blue Mountains portion.