who was the first Mount Everest climber?

Mount Everest, also known to Tibetans as Chomolungma, is
the world's tallest mountain at 8,848 meters (29,029 feet). Until 1885 it was generally
believed to be unclimbable, due to its extreme climate, remote location, and the lower
atmospheric oxygen levels at the summit. The British mounted several attempts in the
early 1920's, including the 1924 expeditions by George Mallory. Mallory and Andrew
Irvine never returned from their attempt at the summit, and Mallory's body was not found
until 1999. It is not known whether these men reached the
summit.

On May 29, 1953, New Zealander Edmund Hillary and
Nepali Tenzing Norgay officially reached the summit and returned safely. For some years
the pair shared credit and refused to say who had reached the summit first, but in his
later years Norgay revealed that it was Hillary.