Stephen Mather Wilderness, Wilderness area in North Cascades National Park Complex, Washington, US

The Stephen Mather Wilderness covers 634,614 acres (256,819 ha) across three units of the North Cascades National Park Complex: North Cascades National Park, Ross Lake National Recreation Area and Lake Chelan National Recreation Area. It is bordered by the Pasayten, Mount Baker, Noisy-Diobsud, Glacier Peak and Lake Chelan-Sawtooth wildernesses. About 390 miles (628 km) of trails cross the area, including a 13-mile (21 km) stretch of the Pacific Crest Trail.

The area was protected in 1988 through the Washington Park Wilderness Act and named after Stephen Mather, the first director of the National Park Service. This designation honored his work in establishing the foundations of wilderness conservation across the United States.

The wilderness reflects American conservation values through its strict regulations prohibiting motorized equipment and mechanical transport to maintain natural conditions.

Weather can shift rapidly and unpredictably, so visitors should check current conditions and prepare accordingly before setting out. Many routes require multi-day treks through remote backcountry terrain, which demands solid physical fitness and experience with wilderness hiking.

The wilderness is bordered by five other wilderness areas: Pasayten to the northeast, Mount Baker to the northwest, Noisy-Diobsud to the west, Glacier Peak to the southwest and Lake Chelan-Sawtooth to the southeast. The Pacific Crest Trail crosses its southeastern corner for about 13 miles (21 km).