in the United States, any of numerous forest areas set aside under federal supervision for the purposes of conserving water, timber, wildlife, fish, and other renewable resources and providing recreational areas for the public. The national forests are administered by the Forest Service in the Department of Agriculture. They numbered 156 by the 21st century and occupy a total area of almost 300,000 square miles (about 770,000 square km) in 40 states and Puerto Rico. They are managed according to the principle of multiple use, whereby various resources—including water, timber, and grasslands—are utilized to serve the nation's interests without reducing the land's capability to produce more.

The U.S. national forests began in 1891 as a system of forest reserves, the establishment of which had been urged by Secretary of the Interior Carl Schurz (Schurz, Carl). President Theodore Roosevelt (Roosevelt, Theodore) created the Forest Service in 1905 and established additional forest reserves. In 1907 the forest reserves were renamed national forests.