Ypsilon Mountain, Mountain summit in the Mummy Range, Rocky Mountain National Park, Colorado, United States

Ypsilon Mountain is a 13,520-foot (4,121 m) summit in the Mummy Range of Rocky Mountain National Park, in Larimer County, Colorado. Its east face holds a Y-shaped snowfield, and the mountain offers several climbing areas for mountaineers and rock climbers. It is most easily reached with Mount Chiquita from a trailhead on Fall River Road to the south.

Ypsilon Mountain was named in 1887 by Mrs. Frederick H. Chapin, who saw a Y-shaped snowfield on its east face and chose the Greek letter upsilon. The peak, 13,520 feet high in the Mummy Range, is climbed mainly from a trailhead on Fall River Road south of the mountain, the same approach used for Mount Chiquita.

The mountain takes its name from its resemblance to the Greek letter Ypsilon, a detail that locals and visitors still reference when describing the peak. This shape-based naming reflects how climbers perceive and remember the landscape.

Visitors access the summit via the Fall River Road trailhead, where several established paths branch off toward the peak. Weather conditions change rapidly at this elevation, so it is wise to start early and prepare for variable terrain along the way.

The Four Aces of Blitzen Ridge presents four distinctive rock formations that challenge climbers with technical passages and vertical sections. This route is known among experienced alpinists for testing both strength and problem-solving skills on exposed terrain.