The Fountain Fire was a large and destructive wildfire in Shasta County, California, United States, in 1992. The fire ignited on August 20 in an act of probable but unattributed arson, and was quickly driven northeast by strong winds. It outpaced firefighters for two days, exhibiting extreme behavior such as long-range spot fires, crown fire runs, and pyrocumulonimbus clouds with dry lightning. The fire was contained after burning for nine days, though work to strengthen and repair fire lines continued for more than two months.

The Fountain Fire burned a total of 63,960 acres (25,880 ha) and destroyed hundreds of homes, primarily in Round Mountain and Montgomery Creek along the State Route 299 corridor. In 1992, it was the third most destructive wildfire in California's recorded history, though it no longer features among the 20 most destructive California wildfires. At a suppression cost of more than $22 million (about $44 million in 2024), it was also for a time the most expensive fire to contain in state history.

At the time, the Fountain Fire was recognized not just as a major disaster, but also as a 'fire of the future'. The devastation the fire left as it moved through private timberlands interspersed with rural communities made it emblematic of the challenges residents and firefighting personnel face in the wildland–urban interface. The Fountain Fire was surpassed by later California wildfires in metrics for losses, but remains notable for its speed, its widespread destruction in multiple communities, and the long-term alteration of the landscape within its footprint.

The Fountain Fire burned in eastern Shasta County, part of the southern extent of the Cascade Range. The area was a secondary forest, having entirely regrown after logging between 1886 and 1923. The forest contained mixed conifers, comprising incense cedar, Douglas fir, sugar pine, and ponderosa pine, among other species. Sixty-five percent of the forest that the Fountain Fire burned was owned and managed by timber companies, including Roseburg Forest Products, Sierra Pacific Industries, and Fruit Growers Supply. Only one percent of the forest was owned by the state or the federal government; the other 34 percent belonged to smaller private landowners.

Both long-term climatic patterns and short-term weather conditions helped create an environment conducive to a large and uncontrollable wildfire in late August 1992. Between 1987 and 1992, California experienced drought of a duration and severity not seen in the state since the 1920s and 1930s. Four of these six years ranked in the driest 10 percent of years by runoff. The stress on forests led to widespread bark beetle infestation.

Several weeks of high temperatures—equal to or exceeding 100 °F (38 °C) for 22 days—preceded the fire in Shasta County. There were also fewer firefighting personnel and equipment available than normal due to an already-active fire season in California; on the Fountain Fire's first day four thousand firefighters were deployed on the destructive Old Gulch Fire in Calaveras County.

Lastly, a critical fire weather pattern developed in Northern California. The influence of an upper-level trough moving onshore in the Pacific Northwest and a strong upper-level jet situated over Northern California created strong flow out of the southwest and Foehn winds on the eastern slopes of the Cascade Range and the Sierra Nevada. Those winds also brought dry air courtesy of the dry slot, a feature often accompanying low-pressure systems. The Northern California Geographical Coordination Center identifies this as a typical critical fire weather setup in northeastern California and the southern Cascades: "Pre-frontal conditions occur when strong, southwesterly or westerly winds are generated by the dry, southern tail of a rapidly moving cold front." In the Fountain Fire's vicinity on August 20, southwest winds blew at up to 25 miles per hour (40 km/h).

The Fountain Fire was first spotted by a fire lookout atop Hogback Mountain in the Shasta-Trinity National Forest at about 12:50 p.m. PDT on August 20. The lookout reported a smoke column behind a ridge, near a historic drinking fountain along Highway 299 (which gave the incident its name). They could not see the actual ignition point of the growing fire, which was confirmed by the Shasta Bear Mountain lookout's cross-check to be about two miles (3.2 km) from the fountain in dry grass off of Buzzard Roost Road, just west of Phillips Road and south of Highway 299. When a resident of Phillips Road spotted the fire shortly before 1:00 p.m., it was already 30 feet (9.1 m) across and it had climbed into the tree canopy.