Sawmill Geyser, Fountain geyser in Upper Geyser Basin, Yellowstone National Park, Wyoming, United States.

Sawmill Geyser is a fountain-type hot spring in the Upper Geyser Basin of Yellowstone National Park. During each eruption, the water shoots about 35 feet (11 meters) into the air and the event lasts between 30 and 50 minutes, with water temperatures reaching about 92 degrees Celsius (198 degrees Fahrenheit).

The geyser was named in 1871 by Antoine Schoenborn of the Hayden Geological Survey, who observed that its rotating water columns resembled a saw blade in motion. The name stuck because of this distinctive resemblance to a lumber mill's mechanical action.

The name Sawmill comes from the water spinning in the crater during eruptions, resembling a rotating saw blade. Antoine Schoenborn of the 1871 Hayden Geological Survey gave the name. Visitors can watch for bubbles rising as the geyser fills and overflows, a sign an eruption is near.

You can watch this geyser from a wooden boardwalk located just about 10 feet (3 meters) away from the spring opening. Plan for some waiting time since eruptions happen every one to three hours when the geyser is actively working.

Sawmill sits about 10 feet off the path in the Upper Geyser Basin and is the largest geyser of the Sawmill Complex. Its eruptions depend on its neighbours: it often follows Spasmodic Geyser, but only if Penta Geyser has not erupted first, since a Penta eruption cuts off Sawmill's water until the basin refills. After a large eruption, other geysers nearby can behave unusually.