Gu Achi Peak, known in O'odham as Ge Aji Doʼag, is a mountain in Arizona's Santa Rosa Mountains on the Tohono O'odham Indian Reservation, about 56 miles west of Tucson. Its name means "big ridge." More than a prominent landform, it holds deep historical importance for the O'odham people. In precolonial times, the peak lay at the center of the Totokwan group's territory, and it may also have been the ceremonial center for northern O'odham groups, linking the mountain to both community life and spiritual traditions.