Mahathir Mohamad was sworn in as Malaysia's next leader following his stunning election victory over the ruling coalition that had governed the Southeast Asian nation for six decades.
Dressed in traditional Malay dress, Mahathir took the oath of office at a ceremony in Kuala Lumpur on Thursday. Malaysia's constitutional monarch, King Sultan Muhammad V, administered the oath.
At 92, Mahathir became the world's oldest head of state.
As he was sworn in, fireworks lit up in the night sky across Kuala Lumpur.
Hundreds of Malaysians lined the road leading to the palace, waving party flags and cheering the veteran politician who previously ruled for 22 years until his retirement in 2003.
Addressing a news conference after the ceremony, Mahathir thanked supporters and said, "Right away, we will have to do a lot of work tomorrow."
Mahathir's alliance of four parties, the Pakatan Harapan or Alliance of Hope, trounced the ruling Barisan Nasional (BN) coalition, which had ruled the country since its independence from the British.
Voters appeared to punish defeated Prime Minister Najib Razak who has been embroiled in a massive corruption scandal for years and also implemented a highly unpopular sales tax.
Earlier in the day, Najib, who ruled Malaysia for nearly a decade, said he accepted the "verdict of the people". He did not attend the swearing-in ceremony at the palace.
The opposition won 121 seats, one more than required for a simple majority, and BN has 79 in the 222-member parliament, according to official results.
Mahathir said he had been assured of support from a raft of parties that would give his government 135 members of parliament.
"This upset ranks up there with Brexit and the Trump election," said Aninda Mitra, a senior sovereign analyst at BNY Mellon Investment Management.
Corruption downfall
Mahathir decided to take on Najib in the wake of the financial scandal and joined the opposition, with many old foes during his previous rule, to defeat him.
The US Department of Justice says $4.5bn was looted from the 1MBD investment fund by associates of the former prime minister between 2009 and 2014, including $700m that landed in Najib's bank account.
Najib denies any wrongdoing.
Mahathir told reporters he will try to make the ringgit currency as steady as possible, and return the billions lost in the 1MDB scandal.
"We believe that we can get most of the 1MDB money back ... We have to increase the confidence of investors in the administration," he said.
The new government will also repeal a goods and services tax introduced by Najib, review foreign investments and abolish "oppressive and unfair" laws, he added.
What's next?
Few had expected Mahathir to prevail against a coalition that has long relied on the support of the country's Malay ethnic majority.
Khoo Ying Hoi, a professor of international and strategic studies at the University of Malaya, said the election "has proved to us that we moved beyond racial politics".
"It's really people power through the ballot," said Khoo.
Mahathir joined hands with jailed political leader Anwar Ibrahim, his one-time deputy with whom he fell out in 1998, and together their alliance exploited public disenchantment.
Mahathir said one of his first actions would be to seek a royal pardon for Anwar. He said he would step aside within the next two years so Anwar could become prime minister.
Anwar's wife, Wan Azizah Wan Ismail, is to be deputy prime minister.
Al Jazeera's Divya Gopalan, reporting from Kuala Lumpur, said Malaysians were still taking stock of the unexpected elections results.
"At the moment, there is a sense of euphoria here," she said. "There has been disillusionment with the previous government with the rise in the cost of living, corruption allegations, so they feel like they have mobilised some kind of change."
