Saint Mary Peak is a prominent 9,351-foot mountain in western Montana's Bitterroot Range, rising steeply above the surrounding landscape in the Selway–Bitterroot Wilderness west of Stevensville. Its summit towers more than 5,000 feet above Big Creek within three miles, making it notable for strong local relief. Runoff from the peak feeds tributaries of the Bitterroot River, linking it to the broader Bitterroot Valley. A popular 3.5-mile trail leads to a summit fire lookout first built in 1931, rebuilt in 1953, and listed on the National Register of Historic Places in 2018. The peak is officially recognized by the United States Board on Geographic Names and lies in a subarctic climate.