Prachanda, 53, who chairs the Communist Party of Nepal, was voted in as premier by the Constituent Assembly on Friday. His party won elections to the assembly in April, with pledges of radical reforms.
"I will remain faithful to the nation and my countrymen, and promise in the name of the people that I will remain faithful to the sovereign nation of Nepal," the new prime minster said at a ceremony held at President Ram Baran Yadav's office in Kathmandu.
In May, the newly elected Constituent Assembly abolished Nepal's Hindu monarchy. The 601-member body, in which the Communist Party has 227 seats, is expected to draft a new constitution in the near future.
Although the premier's real name is Pushpa Kamal Dahal, he continues to use his Maoist rebel name Prachanda (meaning "fierce one"), following the example of other communist leaders, notably Lenin, Stalin and Ho Chi Minh.
