Mount Formidable is a mountain in the North Cascades of Skagit County, in Washington state. Its first ascent was undertaken by members of the original Ptarmigan Traverse, and the peak is a popular climb for parties on the traverse. It was named by early mountaineer Herman Ulrichs in 1935 because of the rugged appearance of its north face. The peak is usually accessed from Cascade Pass via the Ptarmigan Traverse.