BUENOS AIRES — Argentina elected right-wing libertarian Javier Milei as its new president on Sunday, rolling the dice on an outsider with radical views to fix an economy battered by triple-digit inflation, a looming recession and rising poverty.

Mr. Milei, who rode a wave of voter anger with the political mainstream, won by a wider-than-expected margin. He landed some 56% of the vote versus just over 44% for his rival, Peronist Economy Minister Sergio Massa, who conceded.

“The model of decadence has come to an end, there’s no going back,” Mr. Milei said in a defiant speech after the result, while also acknowledging the challenges that face him.

“We have monumental problems ahead: inflation, lack of work, and poverty,” he said. “The situation is critical and there is no place for tepid half-measures.”

In downtown Buenos Aires hundreds of Milei supporters honked horns and chanted his popular refrain against the political elite — “out with all of them” — as rock music played from speakers. Some people set off fireworks as excitement spread.

“We came to celebrate this historic triumph,” said Efrain Viveros, a 21-year-old student from the province of Salta. “I’m honestly ecstatic. Milei represents change, for the better. With Massa we’d have had no future, our future has returned.”

Mr. Milei is pledging economic shock therapy. His plans include shutting the central bank, ditching the peso, and slashing spending, potentially painful reforms that resonated with voters angry at the economic malaise.

“Milei is the new thing, he’s a bit of an unknown and it is a little scary, but it’s time to turn over a new page,” said 31-year-old restaurant worker Cristian as he voted on Sunday.

Mr. Milei’s challenges are enormous. He will have to deal with the empty coffers of the government and central bank, a creaking $44-billion debt program with the International Monetary Fund, inflation nearing 150% and a dizzying array of capital controls.

Some Argentines had characterized the vote as a choice of the “lesser evil”: fear of Mr. Milei’s painful economic medicine versus anger at Mr. Massa and his Peronist party for an economic crisis that has left Argentina deeply in debt and unable to tap global credit markets.

Mr. Milei has been particularly popular among the young, who have grown up seeing their country lurch from one crisis to another.

“Perhaps not everything Milei says I agree with or can identify with but he is our future,” said Irene Sosa, a 20-year-old student celebrating outside his election bunker. “Milei represents a future for young people like me, Massa was everything that is wrong with our country.”

Mr. Milei’s win shakes up Argentina’s political landscape and economic roadmap, and could impact trade in grains, lithium and hydrocarbons. Mr. Milei has criticized China and Brazil, saying he won’t deal with “communists,” and favors stronger US ties.

Despite that, Brazilian President Luiz Inacio Lula da Silva wished Mr. Milei luck and success after the result was announced, adding that it was important democracy was respected.

Former US President Donald Trump congratulated Mr. Milei and said the libertarian would make Argentina great again.

Leftist Colombian President Gustavo Petro, meanwhile, said it was a “sad day” for the region.

‘PROFOUND RUPTURE’
The victory of Milei, a 53-year-old economist and former TV pundit, has broken the hegemony of the two leading political forces on the left and right — the Peronists that have dominated Argentine politics since the 1940s and its main opposition, the Together for Change conservative bloc.

“The election marks a profound rupture in the system of political representation in Argentina,” said Julio Burdman, director of the consultancy Observatorio Electoral, ahead of the vote.

The campaign of Mr. Massa, 51, an experienced political wheeler-dealer, had sought to appeal to voter fears about Mr. Milei’s volatile character and plans to cut back the size of the state. “Milei’s policies scare me,” teacher Susana Martinez, 42, said on Sunday after she voted for Mr. Massa.

Mr. Milei is staunchly anti-abortion, favors looser gun laws and has criticized Argentine Pope Francis. He used to carry a chainsaw in a symbol of his planned cuts but shelved it in recent weeks to help boost his moderate image. — Reuters