Henry's Fork Caldera, Volcanic caldera in Fremont County, Idaho, US.

Henry's Fork Caldera is a volcanic crater in Fremont County in eastern Idaho. It measures about 37 kilometers (23 miles) wide and 29 kilometers (18 miles) long, forming a circular depression within the larger Island Park Caldera.

The Henry's Fork Caldera formed 1.3 million years ago in an eruption of the Yellowstone hotspot that ejected at least 280 cubic kilometers of ash, the Mesa Falls Tuff. That ash covered all of Wyoming and most of Colorado, Nebraska and Kansas. The caldera sits nested inside the older, larger Island Park Caldera, and the two share a rim on the western side.

The caldera lies within Island Park, a region known for its forests, large springs, clear streams, waterfalls, lakes and fishing. Harriman State Park sits inside the caldera, and snowmobiling, fishing, Nordic skiing and wildlife viewing are popular here. The peaks of the Teton Range in neighbouring Wyoming can be seen to the southeast.

The caldera is accessible by car, and visitors can enjoy outdoor activities like Nordic skiing, fishing, and snowmobiling depending on the season. The best time to visit is summer and early fall when roads are generally open and accessible.

The Henry's Fork Caldera is the only caldera of the Yellowstone hotspot whose rim is still clearly visible today, including the later Yellowstone Caldera. Its curved rim can be seen from many spots in the Island Park area, and the Teton Range in Wyoming shows to the southeast.