Bull Lake is an unincorporated community and census-designated place (CDP) in Lincoln County, Montana, United States. It is in the southwestern part of the county, surrounding the lake of the same name. Montana Highway 56 runs along the east side of the lake, leading north 18 miles (29 km) to Troy in the Kootenay River valley and south 19 miles (31 km) to Montana Highway 200 in the Clark Fork valley. Bull Lake was first listed as a CDP prior to the 2020 census.