Sulphur Spring, also known as Crater Hills Geyser, is a geothermal feature in Yellowstone National Park’s Hayden Valley in Wyoming, in the Crater Hills area about 1 mile west of the Grand Loop Road. Though often shown as a spring, Yellowstone’s geothermal catalog identifies it as a geyser. Measurements record a vent temperature of 89 °C and water in the spring of about 79.8 °C, placing it among the park’s high-temperature hydrothermal features.