Seton River, Mountain brook in British Columbia, Canada.

Seton River is a tributary of the Fraser River in British Columbia. It leaves Anderson Lake and runs 3 km east to Seton Lake, then continues 5 km from the foot of Seton Lake to the Fraser at Lillooet. Most of the lower flow is diverted through the Seton Canal to a powerhouse on the Fraser.

The name Seton River was adopted on 6 September 1951, replacing the earlier names Portage Creek and Seton Portage River for the upper stretch and Seton Creek for the lower one. The Seton Dam raised Seton Lake by about 2 m, and since 1961 water from the Bridge River has been diverted into the lake under the Bridge River Power Project. Below the dam most of the flow runs through the Seton Canal to a powerhouse on the Fraser River.

The river's name is recent: the Canadian Geographic Names Board coined "Seton River" in 1950, and locals still call the lower stretch below Cayoosh Creek "Cayoosh Creek" or "Cayoose Creek". That spelling is also the old name of the Sekw'el'wás First Nation, once recorded as the Cayoose Creek Indian Band.

The river's lower course runs 4.4 km from below the Seton Dam to its mouth on the Fraser south of Lillooet, and most of its water is diverted through the Seton Canal to a powerhouse on the Fraser's bank. The Cayoosh Creek joins from the southwest 3 km above the mouth. The upper stretch between Anderson Lake and Seton Lake passes the Seton Portage Historic Provincial Park.

A concrete dam about 18 meters high was built in 1956 and includes a fish ladder alongside a diversion canal that carries water to the nearby Seton Powerhouse. This combination allows salmon to move upstream while simultaneously generating electricity.