Fortress Mountain is a peak in the Cascade Range located about west of Lake Chelan in Chelan/Snohomish Counties, Washington, United States. It straddles the border between the Mount Baker-Snoqualmie National Forest and the Wenatchee National Forest, and is also part of the Glacier Peak Wilderness. Fortress Mountain is the highest point on Chiwawa Ridge, and other notable peaks on this ridge include Napeequa Peak, Buck Mountain, Brahma Peak, Bandit Peak, Mount Berge, and Chiwawa Mountain.