Buchanan is a city in Berrien County in the U.S. state of Michigan. The population was 4,300 at the 2020 census. The city is located at the southeast corner of Buchanan Township, about 5 miles (8.0 km) west of Niles.

Berrien County is a county in the U.S. state of Michigan. It is located at the southwest corner of the state's Lower Peninsula, located on the shore of Lake Michigan and sharing a land border with Indiana. As of the 2020 Census, the population was 154,316. The county seat is St. Joseph.