Fly Geyser, also known as Fly Ranch Geyser is a small geothermal geyser located on private land in Washoe County, Nevada, about 20 miles (32 km) north of Gerlach. Fly Geyser is located near the edge of Fly Reservoir in the Hualapai Geothermal Flats and is approximately 5 feet (1.5 m) high by 12 feet (3.7 m) wide, counting the mound on which it sits.

In June 2016, the non-profit Burning Man Project purchased the 3,800 acres (1,500 ha) Fly Ranch, including the geyser, for $6.5 million. The Burning Man Project began offering limited public access to the property in May 2018. The geyser contains thermophilic algae, which flourish in moist, hot environments, resulting in multiple hues of green and red, coloring the rocks.