O'Sullivan Peak, also known as Sunrise Peak, is an 11,275-foot-elevation (3,437-meter) mountain summit located in Salt Lake County, Utah, United States.

O'Sullivan Peak is located 15 miles (24 km) southeast of downtown Salt Lake City in the Twin Peaks Wilderness on land managed by Wasatch–Cache National Forest.

[4] The peak is set in the Wasatch Range which is a subset of the Rocky Mountains.

Topographic relief is significant as the summit rises 4,475 feet (1,364 meters) above Little Cottonwood Canyon in 1.4 mile (2.25 km).

This mountain's toponym was officially adopted in 1978 by the United States Board on Geographic Names to remember Timothy H. O'Sullivan (1840–1882), civil war and western frontier photographer who visited this area as the official photographer of the King Survey and Wheeler Survey.