Modoc is an unincorporated community in Randolph County, Illinois, United States, located four miles southeast of Prairie du Rocher under the bluffs of the Mississippi River.
The Modoc Rock Shelter, a U.S. National Historic Landmark, is located near Modoc and the Ste. Genevieve-Modoc Ferry across the Mississippi River connects Modoc and the surrounding communities with Ste. Genevieve, Missouri.
The area's population was 221 at the 2000 census.