The Yellowstone fires of 1988 collectively formed the largest wildfire in the recorded history of Yellowstone National Park in the United States. Starting as many smaller individual fires, the flames quickly spread out of control due to drought conditions and increasing winds, combining into one large conflagration which burned for several months. The fires almost destroyed two major visitor destinations and, on September 8, 1988, the entire park closed to all non-emergency personnel for the first time in its history. Only the arrival of cool and moist weather in the late autumn brought the fires to an end. A total of 793,880 acres (3,213 km2), or 36 percent of the park, was affected by the wildfires.Thousands of firefighters fought the fires, assisted by dozens of helicopters and fixed-wing aircraft which were used for water and fire retardant drops. At the peak of the effort, more than 9,000 firefighters were assigned to the park. With fires raging throughout the Greater Yellowstone Ecosystem and other areas in the western United States, the staffing levels of the National Park Service and other land management agencies were inadequate for the situation; more than 4,000 U.S. military personnel were soon brought in to assist in wildfire suppression efforts. The firefighting effort cost $120 million ($260 million in 2022). Losses to structures were minimized by concentrating firefighting efforts near major visitor areas, keeping property damage down to $3 million ($7 million as of 2022). No firefighters died while fighting the Yellowstone fires, though there were two fire-related deaths outside the park.

Before the late 1960s, fires were generally believed to be detrimental for parks and forests, and management policies were aimed at suppressing fires as quickly as possible. However, as the beneficial ecological role of fire became better understood in the decades prior to 1988, a policy was adopted of allowing natural fires to burn under controlled conditions, which proved highly successful in reducing the area lost annually to wildfires.

In contrast, in 1988, Yellowstone was overdue for a large fire, and, in the exceptionally dry summer, many smaller "controlled" fires combined. The fires burned discontinuously, leaping from one patch to another, leaving intervening areas untouched. Intense fires swept through some regions, burning everything in their paths. Tens of millions of trees and countless plants were killed by the wildfires, and some regions were left looking blackened and dead. However, more than half of the affected areas were burned by ground fires, which did less damage to hardier tree species. Not long after the fires ended, plant and tree species quickly reestablished themselves, and native plant regeneration has been highly successful.

The Yellowstone fires of 1988 were unprecedented in the history of the National Park Service, and led to many questions about existing fire management policies. Media accounts of mismanagement were often sensational and inaccurate, sometimes wrongly reporting or implying that most of the park was being destroyed. While there were temporary declines in air quality during the fires, no adverse long-term health effects have been recorded in the ecosystem and, contrary to initial reports, few large mammals were killed by the fires, though there was a subsequent reduction in the number of moose.