Williamson Mountain, elevation , is a peak in the Cascade Range in the U.S. state of Oregon. It is named after Lt. Robert S. Williamson, who with Lt. Philip Sheridan took part in the Pacific Railroad Surveys in central Oregon in 1855. The United States Board on Geographic Names approved the name in 1931. Before that, the peak was known by its Chinook Jargon name of Leloo Mountain (Wolf Mountain), derived from the French le loup (the wolf).