Arapaho National Forest is a National Forest located in north-central Colorado, United States. The facility is managed jointly with the Roosevelt National Forest and the Pawnee National Grassland from the United States Forest Service office in Fort Collins, Colorado. It has a wildlife refuge which manages a protection for all birds and mammals. The combined facility of 1,730,603 acres is denoted as ARP by the Forest Service. Separately, Arapaho National Forest consists of 723,744 acres.
The forest is located in the Rocky Mountains, straddling the continental divide in the Front Range west of Denver. It was established on July 1, 1908, by President Theodore Roosevelt and named for the Arapaho tribe of Native Americans which previously inhabited the Colorado Eastern Plains. The forest includes part of the high Rockies and river valleys in the upper watershed of the Colorado River and South Platte River. The forest is largely in Grand and Clear Creek counties, but spills over into neighboring Gilpin, Park, Routt, Jackson, and Jefferson counties. There are local ranger district offices located in Granby and Idaho Springs.