Reinhold Messner is an Italian mountaineer famous for being the first to climb all 14 mountains over 8,000 meters without oxygen. As one of the greatest climbers ever, he has climbed many peaks without oxygen support, including Nanga Parbat known for its massive vertical wall. In one of his most famous adventures, Messner achieved the incredible feat of climbing Mount Everest alone and without oxygen after first summiting it with a friend using the same technique.