The President of Sikkim Krantikari Morcha (SKM) Prem Singh Tamang also popularly known as PS Golay, took oath as the Chief Minister of Sikkim on Monday.
The 51-year-old Golay was administered the oath of office by Governor Ganga Prasad at a function at Paljor Stadium here.
Golay did not contest the polls so he is not a member of the state assembly at present.
Hundreds of SKM supporters who were at the stadium cheered the 51-year-old party chief when he was taking the oath in Nepali language.
Former chief minister Pawan Kumar Chamling and senior Sikkim Democratic Front (SDF) leaders were conspicuous by their absence at the swearing-in.
The Chamling government was toppled by the Sikkim Krantikari Morcha after over 24 years.
The SKM, founded in 2013, won a slender majority in the 32-member Sikkim Legislative Assembly by bagging 17 seats against 15 won by the Sikkim Democratic Front( SDF).