He will take over as the 32nd state Chief Minister.
Supporters of Adityanath were seen shouting 'Yogi,Yogi' outside Lok Bhawan in the state capital.
Adityanath, a five-time MP from the Gorakhpur constituency, was the youngest member of the 12th Lok Sabha at the age of 26.
Currently, Adityanath serves as the Mahant of Guru Gorakhnath Temple in Gorakhpur, following the death of Mahanth Aavaidyanath on September 12, 2014.
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