Boiling River, Natural hot spring in Yellowstone National Park, United States.

The Boiling River is a hot spring in Park County, Wyoming, at 1,731 metres in a valley 5.4 km north of Gardiner. Thermal water from Mammoth Hot Springs enters the cold Gardner River, and the mixing creates varied temperatures along the stream.

The Boiling River sits in a valley in Park County, Wyoming, at 1,731 metres, 5.4 km north of Gardiner. The surrounding area is almost uninhabited, with fewer than two people per square kilometre. The site lies in a region of mineral resources, and the local climate is hemiboreal, with January averages of −14 °C and July averages of 20 °C.

The spring sits at 1,731 m in a valley of Park County, Wyoming, about 5.4 km north of Gardiner, Montana, where thermal water from Mammoth Hot Springs meets the cold Gardner River. The surrounding land is mostly sagebrush steppe, and fewer than two people per square kilometre live in the area.

The site is best visited in early morning or late afternoon when fewer people are around. Access to swimming areas remains limited, so visitors should check current access information before arriving.

The Boiling River is a tributary of the Gardner River, not a spring itself. It rises at 1,731 metres in a valley where the surrounding terrain reaches 2,284 metres, and it lies 5.4 km north of Gardiner, Montana.