The Stephen Mather Wilderness is a 634,614 acres (256,819 ha) wilderness area honoring Stephen Mather, the first director of the National Park Service. It is located within North Cascades National Park, Lake Chelan National Recreation Area, and Ross Lake National Recreation Area in the North Cascade Range of Washington, United States. It is bordered by the Pasayten Wilderness to the northeast, the Mount Baker Wilderness to the northwest, the Noisy-Diobsud Wilderness to the west, the Glacier Peak Wilderness to the southwest, and the Lake Chelan-Sawtooth Wilderness to the southeast.