Sun River is a census-designated place (CDP) in Cascade County, Montana, United States. The population was 124 at the 2010 census. It is part of the Great Falls, Montana Metropolitan Statistical Area.
Sun River is located at 47°31′55″N 111°43′47″W (47.531915, -111.729648).
According to the United States Census Bureau, the CDP has a total area of 1.8 square miles (4.7 km2), all land.
As of the census of 2000, there were 500 people, 230 households, and 58 families residing in the CDP. The population density was 98.8 people per square mile (27.9/km2). There were 65 housing units at an average density of 35.8 per square mile (13.9/km2). The racial makeup of the CDP was 96.95% White, 2.29% Native American, and 0.76% from two or more races.
There were 58 households, out of which 27.6% had children under the age of 18 living with them, 53.4% were married couples living together, 5.2% had a female householder with no husband present, and 36.2% were non-families. 31.0% of all households were made up of individuals, and 8.6% had someone living alone who was 65 years of age or older. The average household size was 2.26 and the average family size was 2.84.