Montrose County is a county located in the U.S. state of Colorado. As of the 2020 census, the population was 42,679. The county seat is Montrose, for which the county is named.

Montrose is a home rule municipality that is the county seat and the most populous municipality of Montrose County, Colorado, United States. The city population was 20,291 at the 2020 census, within a total area of 18.5 square miles. The main road that leads in and out of Montrose is U.S. Highway 50. The city is located in western Colorado, in the Uncompahgre Valley, and is an economic, labor, and transportation waypoint for the surrounding area. Montrose is the second-largest city in western Colorado, after Grand Junction.