Prairie du Rocher is a village in Randolph County, Illinois, United States. Founded in the French colonial period in the American Midwest, the community is located near bluffs that flank the east side of the Mississippi River along the floodplain often called the "American Bottom". The population was 502 at the 2020 census. Prairie du Rocher is one of the oldest communities in the 21st century United States that was founded as a French settlement.