St. Joseph County is a county located in the U.S. state of Michigan, on the central southern border with Indiana. As of the 2020 United States Census, the population was 60,939. The county seat is Centreville.

The St. Joseph River is a tributary of Lake Michigan with a length of 206 miles (332 km). The river flows in a generally westerly direction through southern Michigan and northern Indiana, United States, to its terminus on the southeast shore of the lake. It drains a primarily rural farming area in the watershed of Lake Michigan. It was enormously important to Native Americans and greatly aided in the colonial exploration, settlement and administration of New France and the nascent United States as a canoe route between Lake Michigan and the watershed of the Mississippi River.