Governor Ram Naik administered the oath of office and secrecy to Adityanath and his Cabinet at a function in Lucknow's Smriti Upvan here.
Prime Minister Narendra Modi and party president Amit Shah were in attendance.
Maharashtra Chief Minister Devendra Fadnavis, newly-elected Goa Chief Minister Manohar Parrikar, Chhattisgarh Chief Minister R. Singh, Madhya Pradesh Chief Minister Shivraj Singh Chouhan and Andhra Pradesh Chief Minister N. Chandrababu Naidu and Union Ministers Nitin Gadkari, Uma Bharti and Rajnath Singh also attended the ceremony.
Adityanath, a five-time Lok Sabha MP from Gorakhpur, was unanimously elected as the BJP Legislature Party leader at a meeting of the newly-elected MLAs in Lucknow last evening. He, later, met the Governor and staked claim to form the government in the state.
Given his image as a champion of the BJP's 'Hindutva' establishment in the state, Adityanath's election as UP Chief Minister has set many tongues wagging in political circles, primarily because of the statements he gave before his appointment as the Chief Minister of the state.
Talking to reporters at Raj Bhavan, he said, he would follow Prime Minister Narendra Modi's slogan 'Sab ka saath, Sab ka vikas' and ensure all-round development of the state.
Senior party leader and Union Minister M. Venkaiah Naidu, who was the central observer at the Legislature Party meeting, said it was a watershed moment for the BJP and it has become a common man's party. He said, the mandate is for development and against corruption and black money.
In the recently-held polls in the state, the BJP bagged 312 seats, and its allies 13, taking the alliance's tally to 325 in the 403-member Assembly.
Meanwhile, Adityanath has called on his followers and admirers to maintain law and order during their celebrations, while giving full freedom to the state police to take action on those who create ruckus.
"There should be no chaos in the name of celebrations. Police must deal swiftly and firmly with miscreants," he said.
Following the Chief Minister designate's orders, all the District Senior Superintendent of Police (SSP) have been called to ensure law and order is maintained.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)