The Selway-Bitterroot Wilderness is a protected wilderness area in the states of Idaho and Montana, in the northwestern United States. At 1.3 million acres (5,300 km²), it is one of the largest designated wilderness areas in the United States (14th overall, but third-largest outside Alaska). It spans the Bitterroot Mountain Range, on the border between Idaho and Montana. It covers parts of Bitterroot National Forest, Clearwater National Forest, Lolo National Forest, and the Nez Perce National Forest. The Frank Church-River of No Return Wilderness Area is immediately to its south, separated only by a dirt road (the Magruder Corridor). Together with adjoining public land, the two wilderness areas form a five million acre (20,000 km²) wild region.