Trinity Mountain is the highest point of the Trinity Mountains, a subrange of the Boise Mountains in Boise National Forest in Idaho. Its summit rises to 9,451 feet, making it a prominent peak in the forested mountains northeast of the South Fork Boise River drainage. Located within the watershed of the South Fork Boise River, it is part of the river system that drains this section of central Idaho. Trinity Mountain stands 11.63 miles from Steel Mountain, its line parent, and has a topographic prominence of 2,371 feet.