Ishi Wilderness, Protected wilderness area in Tehama County, United States.

Ishi Wilderness is a 41,339-acre protected area in the Shasta Cascade foothills of Lassen National Forest, about 20 miles east of Red Bluff. East-west ridges frame rugged river canyons cut by Deer Creek and Mill Creek, with ridges reaching 4,000 feet. Its slopes show basalt outcroppings, caves and pillar lava formations, and a large triangular bluff of rust-orange and tan eroded rock rises above a band of green trees.

The Yahi-Yana people lived here for thousands of years until displacement began in the 1800s. It became an official protected area in 1984 through legislation meant to preserve the landscape and its cultural heritage.

The name was given by anthropologist Alfred L. Kroeber to Ishi, the last surviving member of the Yahi Yana tribe, who had lived in the area for over three thousand years. After 1850, settlers killed all but a few Yahi, who hid in the wild country. The Forest Service asks visitors to respect the Yahi Yana record; all archaeological sites and artifacts are protected by federal law.

The area has hiking trails through forests and along streams where visitors can explore on foot. Spring and fall offer the most comfortable conditions, with moderate temperatures and good trail accessibility.

The Tehama deer herd, California's largest migratory deer herd, winters in the wilderness. A State Game Refuge where hunting is not permitted covers most of the area, while the Bureau of Land Management manages a small 240-acre portion. Raptors such as hawks, eagles, falcons and owls nest in the rock cliffs.