Lake Lou Yaeger is a 1,300-acre (530 ha) reservoir located in Montgomery County, Illinois.

Created by damming the West Fork of Illinois's Shoal Creek, it was built for recreation, sport fishing, and flood control purposes.

The fish yield is enjoyed by many species; bald eagles began to nest at the lake in 2005.

Boaters enjoy the absence of both speed and power limits such as are enforced on many other lakes in central and southern Illinois.

The municipality of Litchfield operates the lake's largest park, the 266-acre (108 ha) Shoal Creek Conservation Area.