Shawnee National Forest, National forest in southern Illinois, United States.

Shawnee National Forest is a United States National Forest in the Shawnee Hills of southern Illinois, with about 498,615 acres of federally managed land across nine counties. Its canopy of rounded hardwood and pine crowns rolls over low hills, and the southern margin of the Illinoian ice sheet lay within the forest area. Little Grand Canyon, cut more than 200 feet deep toward the Big Muddy River, shelters relict Arctic plants.

President Franklin D. Roosevelt declared the Illini and Shawnee Purchase Units the Shawnee National Forest in September 1939. Most land added in its first decade was exhausted farmland, and Civilian Conservation Corps crews planted pines through the 1930s and 1940s to check erosion and rebuild soil. A new Forest Management Plan followed in 2006.

The forest takes its name from the Shawnee, but the land was bought and replanted by newcomers: in the 1930s and 1940s Civilian Conservation Corps crews planted pines on exhausted farmland to stop erosion and rebuild the soil. The 2016 America the Beautiful quarter honoured the forest, and the 2017 eclipse drew crowds for two minutes 44 seconds of totality.

Visitor information and detailed trail maps are available at the forest administration office in Harrisburg. Before visiting, check local conditions and access guidelines as some areas may have seasonal closures or restrictions.

Shawnee National Forest appeared on the 31st coin of the America the Beautiful Quarters series in 2016. During the August 21, 2017 solar eclipse, the forest offered viewers two minutes 44 seconds of totality; in 2024 it offered four minutes and seven seconds.