Climbing some of the world’s tallest mountains is already an extraordinary feat, but doing so without supplementary oxygen is a challenge reserved for the boldest and most accomplished mountaineers.  Scaling peaks above 26,000 feet, known as the “death zone,” means entering altitudes where the human body struggles to survive.  Oxygen levels at these heights are about a third of what they are at sea level, pushing the limits of endurance and willpower.  For decades, climbers have tested themselves against nature’s giants to prove what is humanly possible.  This list highlights the tallest mountains ever climbed without oxygen, recounting their history, size, unique details, and the brave souls who dared to ascend them under the most extreme conditions.

#1: Mount Everest – 29,032 feet

Mount Everest, towering at 29,032 feet, is not only the tallest mountain in the world but also the most iconic.  Located in the Himalayas on the border of Nepal and Tibet, Everest was first summited without supplemental oxygen in 1978 by Reinhold Messner and Peter Habeler.  This was a monumental achievement that many at the time thought impossible.  At such altitudes, the body begins to shut down as it is starved of oxygen, yet Messner and Habeler proved human resilience could overcome nature’s limits.  Everest is a colossal pyramid of snow, ice, and rock, but it’s also a place of history, spiritual significance, and tragedy.  The Sherpa people, who call it “Chomolungma” or “Goddess Mother of the World,” have long revered it.  Interestingly, the summit itself is a tiny plateau about the size of a dining table.  Reinhold Messner, later recounting his ascent, described it as an almost out-of-body experience, where he felt he was “climbing into the sky.”  Today, Everest attracts thousands of climbers annually, yet its first oxygen-free summit remains one of the most legendary achievements in mountaineering history.

#2: K2 – 28,251 feet

K2, also known as “Savage Mountain,” stands at 28,251 feet and is the second-highest mountain in the world, located in the Karakoram range on the border between Pakistan and China.  Unlike Everest, K2 is known for its extreme difficulty, making it far less summited and far more dangerous.  Achieving this climb without oxygen is considered one of the greatest challenges in the world. In 2004,  Italian climber Walter Bonatti described K2 as the “most terrible” of all climbs because of its treacherous rock formations, sheer slopes, and unpredictable weather.  The first successful ascent without oxygen was completed in 1978 by Louis Lachenal and Maurice Herzog, who faced brutal winds and freezing temperatures.  Unlike Everest, K2 lacks commercial climbing routes, and its technical difficulty means that even the world’s best climbers must prepare for a harrowing journey.  The mountain’s lore includes tragic stories like the 2008 disaster, where 11 climbers perished in a single day. Despite its danger, the peak has an undeniable allure for purists of mountaineering.

#3: Kangchenjunga – 28,169 feet

At 28,169 feet, Kangchenjunga, located on the border of Nepal and India, is the third-highest mountain in the world and the highest in India.  Its name means “Five Treasures of Snow,” referring to the five prominent peaks that form the massif.  Kangchenjunga remained unclimbed until 1955 when British climbers Joe Brown and George Band reached the summit.  Out of respect for local tradition, they stopped a few feet short of the true summit, a practice still honored today.  Climbing Kangchenjunga without oxygen is an exceptional accomplishment, as its steep ridges, unpredictable avalanches, and remoteness create extraordinary challenges.  Reinhold Messner climbed it oxygen-free in 1982, describing it as an “isolated, wild giant.”  The mountain is revered by locals, with many myths surrounding its deities and guardian spirits.  While Kangchenjunga lacks the fame of Everest, its wild beauty and cultural significance make it one of the most majestic peaks in the world.

#4: Lhotse – 27,940 feet

Lhotse, standing at 27,940 feet, is the fourth-highest mountain in the world and lies adjacent to Mount Everest, connected via the South Col.  The name “Lhotse” translates to “South Peak” in Tibetan, and the mountain shares much of Everest’s terrain and climbing routes.  In 1986, the Swiss alpinist Erhard Loretan completed the climb without oxygen, adding Lhotse to his remarkable list of achievements.  What makes Lhotse particularly challenging is the infamous Lhotse Face, a steep wall of ice that climbers must scale at high altitudes.  Climbers often face extreme fatigue and frostbite due to the mountain’s exposure to strong winds and freezing temperatures.  Lhotse’s proximity to Everest sometimes causes it to be overshadowed, but climbers regard it as a formidable challenge requiring technical skill and endurance.

#5: Makalu – 27,838 feet

Makalu, rising to 27,838 feet, is a striking pyramid-shaped mountain located 12 miles from Everest.  It is considered one of the most difficult 8,000-meter peaks due to its steep pitches, knife-edge ridges, and exposed terrain.  The first ascent without oxygen was achieved by French climbers Lionel Terray and Jean Couzy in 1955. Makalu is infamous for its “final summit pyramid,”  where climbers must navigate narrow, rocky ridges while braving the thin air of the death zone. Its isolation adds to its mystique, with fewer climbers attempting it compared to other giants.  Reinhold Messner, who also climbed Makalu without oxygen, noted that it required more technical precision than Everest.  The mountain’s remote beauty and sharp ridges make it a true test for purists of alpine climbing.

#6: Cho Oyu – 26,906 feet

Cho Oyu, at 26,906 feet, is the sixth-highest mountain in the world and one of the most accessible of the 8,000-meter peaks.  Located near the Nepal-Tibet border, its name means “Turquoise Goddess.”  While Cho Oyu is often used for acclimatization due to its relatively less technical routes, climbing it without oxygen remains a grueling achievement.  In 1984, Swiss climbers Hannes Kästle and Fritz Luchsinger made history by reaching its summit without supplemental oxygen.  The summit offers a spectacular view of Everest and the surrounding peaks.  Cho Oyu’s slightly gentler slopes make it an ideal goal for climbers aiming to test themselves in high-altitude conditions without risking their lives on more technical peaks.

#7: Dhaulagiri – 26,795 feet

Dhaulagiri, standing at 26,795 feet, is the seventh-highest mountain in the world and one of the most imposing peaks in Nepal.  Its name translates to “White Mountain” in Sanskrit, a fitting description of its snow-covered slopes and isolated beauty.  Dhaulagiri was first climbed in 1960, but scaling it without oxygen remained elusive until climbers such as Reinhold Messner began to attempt it in the 1970s.  The mountain is infamous for its steep, avalanche-prone terrain and extreme weather changes, making it one of the most dangerous peaks.  Dhaulagiri’s isolation means fewer climbers attempt it compared to Everest or K2, but those who do are drawn by its raw, untamed nature.  Messner, who climbed it without oxygen in 1985, famously described Dhaulagiri as “a lonely, immense snowdrift where time seems to stop.”  The challenging conditions and isolation make a successful ascent without oxygen an extraordinary witness to skill and endurance.

#8: Manaslu – 26,781 feet

Manaslu, rising to 26,781 feet in the Nepalese Himalayas, is the eighth-highest mountain in the world.  Its name means “Mountain of the Spirit,” reflecting its significance to local cultures and its serene, yet imposing presence.  Manaslu is known for its massive ridges and steep slopes, which test even the most seasoned climbers.  The first successful ascent without oxygen was completed in 1983 by Jerzy Kukuczka, the legendary Polish mountaineer. Kukuczka, known for his endurance, remarked on the intense difficulty of ascending Manaslu’s summit ridge while battling the thin air.  The mountain’s relative remoteness and lack of commercialization make it appealing to climbers who seek solitude and a raw challenge.  However, avalanches are a constant danger, with Manaslu earning a reputation for being unforgiving. Despite its risks, its breathtaking views and spiritual significance continue to draw climbers who respect both its beauty and its challenges.

#9: Nanga Parbat – 26,660 feet

Nanga Parbat, towering at 26,660 feet in Pakistan, is the ninth-highest mountain in the world. Known as the “Killer Mountain,” Nanga Parbat has a long history of perilous expeditions and fatalities.  Its sheer vertical rises and formidable weather patterns make it one of the most dangerous mountains to climb, particularly without supplemental oxygen.  The mountain’s first oxygen-free ascent was achieved by Hermann Buhl in 1953, in what remains one of the most legendary solo climbs in history.  Buhl’s remarkable climb involved over 40 hours of continuous climbing, much of it without food or shelter.  Nanga Parbat’s Rupal Face, one of the tallest rock walls in the world, adds to the mountain’s intimidating reputation.  Climbers face extreme isolation, unpredictable avalanches, and brutal cold.  Despite its challenges, Nanga Parbat remains an iconic peak that has tested the mettle of some of the greatest mountaineers, cementing its place in mountaineering lore.

#10: Annapurna I – 26,545 feet

At 26,545 feet, Annapurna I is the tenth-highest mountain in the world and among the most dangerous.  Located in the Annapurna Massif of Nepal, its name means “Goddess of the Harvests,” and it holds deep cultural significance for the region’s people.  The first ascent of Annapurna I without oxygen was achieved by Reinhold Messner in 1985, a feat that was especially remarkable given Annapurna’s reputation for frequent avalanches and unpredictable weather.  The mountain has one of the highest fatality rates among the 8,000-meter peaks, making any ascent an immense challenge. Annapurna’s south face, an almost vertical wall of ice and rock, has become a legendary route in climbing history.  Interestingly, Annapurna was the first 8,000-meter peak to be summited in 1950 by a French team led by Maurice Herzog, though the climb left Herzog and his team with severe frostbite.  Annapurna’s history is filled with triumph and tragedy, making it a peak that symbolizes both the risks and rewards of extreme mountaineering.

Climbing the tallest mountains on Earth without oxygen is one of the most remarkable achievements in human endurance and resilience.  These peaks, from the iconic Everest to the perilous Annapurna, present unique challenges that test the physical and mental limits of climbers.  Whether through dangerous ridges, avalanches, or sheer altitude, each mountain on this list demands respect, courage, and preparation.  The stories of those who have dared to ascend these giants without supplemental oxygen serve as a confirmation to the indomitable human spirit and our relentless pursuit of exploration and achievement.  These mountains will continue to stand as monuments to both nature’s power and humanity’s desire to conquer the impossible.