Arguably for the contrarians, Tenzing Norgay was the first. The facile explanation would be something along the lines of because he led the way or he only stepped aside at the last moment so that Edmund Hillary, the New Zealand beekeeper, could overtake him in order to summit first. What is not factored into this superficial comment is that without Hillary’s finance, determination & wherewithal Tenzing would never have set foot upon the summit. Aside from Tenzing could there indeed have been an earlier person?
Even though the Tibetans & Nepalese had occupied the area adjacent to Chomolungma or Sagarmāthā, as they respectively called Mount Everest for millennia, both are unlikely candidates for two very cogent reasons: technological and religious aside from the fact that Tenzing Norgay had already attempted the climb six times previously and failed. The technological reason is that the majority of climbers require bottled oxygen in order to climb the last 3000 feet. A number of people have attempted a natural climb but that is an extreme rarity even for Sherpas. Even with supplementary oxygen, the average climber is at the limit of their oxygen endurance.
Main picture: Conrad Anker climbing Everest