Climbers who ascend higher than 26,000 feet on Mount Everest enter the death zone. In this area, oxygen is so limited that the body's cells start to die, and judgment becomes impaired. Climbers may also experience heart attack, stroke, or severe altitude sickness.

The "Death Zone" on Mount Everest refers to the region above 8,000 meters (26,247 feet), where the atmospheric pressure is so low that there is not enough oxygen for humans to breathe for an extended period. At this altitude, the oxygen level is approximately one-third of what it is at sea level. In this zone, the human body cannot acclimatize; instead, it begins to die minute by minute. Digestion stops, the brain and lungs can swell (HACE and HAPE), and physical exertion becomes nearly impossible without supplemental oxygen. Most climbers attempt to spend as little time as possible here, usually fewer than 16 to 24 hours, as prolonged exposure leads to extreme frostbite, exhaustion, and cognitive failure. In 2026, despite advancements in high-altitude gear and more efficient "bottled" oxygen systems, the Death Zone remains the site of the majority of fatalities on the mountain, as even a small delay in a "summit push" can be fatal due to the body's rapid deterioration in the oxygen-starved, sub-zero environment.