Cascade County is a county located in the U.S. state of Montana. As of the 2020 census, the population was 84,414, making it the fifth-most populous county in Montana. Its county seat is Great Falls.

Great Falls is the third most populous city in the U.S. state of Montana and the county seat of Cascade County. The population was 60,442 according to the 2020 census. The city covers an area of 22.9 square miles (59 km2) and is the principal city of the Great Falls, Montana, Metropolitan Statistical Area, which encompasses all of Cascade County. The Great Falls MSA's population stood at 84,414 in the 2020 census.