The 41-year-old Kogen Kamahori’s endurance test made him a living form of the Buddha according to his temple’s beliefs, the Asahi newspaper reported.
He was the first person to complete the test in eight years, Japanese media said.
The monk emerged from a training facility at Mount Hieizan, a holy mountain in western Japan dotted with temples, to be greeted by some 600 onlookers and members of the media.
Dressed in a white robe, he appeared shortly before 2:00 am (1700 GMT), assisted by fellow monks.
The programme is considered the toughest part of a seven-year training that includes a total of 1,000 non-consecutive days walking around the mountain in a bid to achieve enlightenment.
He started in 2011 and had completed 700 days of walking before beginning his fast. He is expected to finish the mountain walk in the fall of 2017.