Matekane was sworn-in by Chief Justice Sakoane Sakoane to wild cheers from thousands of supporters.
He pledged to introduce a raft of measures to “make Lesotho great again” by attracting investment and replenishing the government’s coffers, which are believed to be almost dry.
“The government of Lesotho vows that it will be open to foreign direct investment,” the new premier said.
The diamond magnate was appointed prime minister after his Revolution for Prosperity (RFP) won the most seats in general elections held on October 7.
The RFP, however, fell short of securing an absolute majority in the country’s 120-member parliament and had to form a coalition government with two opposition parties.
The swearing in ceremony was witnessed by Lesotho’s King Letsie III and several international leaders.
Others who attended the ceremony were Botswana’s President Mokgweetsi Masisi, President Cyril Ramaphosa of South Africa, Zambia’s President Hichilema Hakainde and Commonwealth secretary general Patricia Scotland.