The Three Sisters Wilderness is a wilderness area in the Cascade Range, within the Willamette and Deschutes National Forests in Oregon, United States. It comprises 286,708 acres (1,160.27 km2), making it the second largest wilderness area in Oregon, after the Eagle Cap Wilderness. It was established by the United States Congress in 1964 and is named for the Three Sisters volcanoes. The wilderness boundary encloses the Three Sisters as well as Broken Top, which is southeast of South Sister.

The Willamette National Forest is a National Forest located in the central portion of the Cascade Range of the U.S. state of Oregon. It comprises 1,678,031 acres (6,790.75 km2). Over 380,000 acres are designated wilderness which include seven major mountain peaks. There are also several National Wild and Scenic Rivers within the forest. The forest is named for the Willamette River, which has its headwaters in the forest. The forest's headquarters are located in the city of Springfield. There are local ranger district offices in McKenzie Bridge, Detroit, Sweet Home, and Westfir.