Harriman State Park is a state park in eastern Idaho, USA. It is located on an 11,000-acre (45 km2) wildlife refuge in the Greater Yellowstone Ecosystem and is home to an abundance of elk, moose, sandhill cranes, trumpeter swans, and the occasional black or grizzly bear. Two-thirds of the trumpeter swans that winter in the contiguous United States spend the season in Harriman State Park. The land was deeded to Idaho for free in 1977 by Roland and W. Averell Harriman, whose insistence that the state have a professional park managing service helped prompt the creation of the Idaho Department of Parks and Recreation in 1965.
The park opened to the public in 1982. It is located in Fremont County, 3 miles (4.8 km) south of Island Park, Idaho. Henry's Fork, a world-famous fly-fishing stream, winds through the meadows of Harriman State Park. In winter, many of its roads and trails are groomed for cross country skiing.
The park is located within a geological feature called a caldera, the Henry's Fork Caldera. Friends of Harriman State Park, Inc. is a 501c3 organization dedicated to community projects that directly benefit Harriman State Park of Idaho. Friends of Harriman State Park was formed in the winter of 2010 after the announcement by the State of Idaho of the need to cut park funding completely and eventually dissolve the Idaho Department of Parks and Recreation into another state agency.