Mr Macri has promised to lead by "listening more and speaking less" Photo: AFP
By BBC News
Conservative Mauricio Macri has been confirmed as the winner in Argentina's presidential elections, as his ruling party opponent conceded.
With almost all votes counted, Mr Macri had 52% to Daniel Scioli's 48%.
Loud cheers erupted at Mr Macri's campaign headquarters after TV exit polls suggested he had won. Mr Macri, the mayor of Buenos Aires, lost to Mr Scioli, who is the governor of Buenos Aires province, in the first round of voting in October.
But neither candidate managed to win the vote outright, forcing a run-off - the first in the country's history - and Mr Scioli lost ground to his rival in the month since.
Mr Macri's victory will be the first in more than a decade for Argentina's centre-right opposition.
He went into Sunday's vote with a comfortable lead in opinion polls, and campaigned on pledges to bring new investment into the ailing economy, tackle crime and fight corruption.
The son of one of Argentina's richest men, he had a long career in business before entering politics.
A close ally of current President Cristina Fernandez de Kirchner, Mr Scioli had been expected to win by a greater margin in October.