Centre-left opposition candidate Alberto Fernández has been elected president of Argentina in a vote dominated by economic concerns.
Mr Fernández secured more than the 45 per cent of the vote needed to win, beating conservative incumbent Mauricio Macri.
Raucous crowds gathered at Mr Fernández's election headquarters to celebrate the result, according to a BBC report.
The vote was held amid an economic crisis that has left a third of Argentina's population in poverty.
Mr Macri had trailed behind his challenger in pre-election polls and was trounced by the opposition in primary elections in August.
He conceded defeat on Sunday night. Congratulating his political rival, he said he had invited Mr Fernández to the presidential palace on Monday to discuss an orderly transition.
Mr Fernández later told supporters he would collaborate with the outgoing president "in every way we can", according to Reuters.
With more than 90 per cent of ballots counted, Mr Fernández had 47.79 per cent of the vote, compared to Mr Macri's 40.71 per cent.
To win in the first round, a candidate needs at least 45 per cent of the vote, or 40 per cent and a 10-point lead over the second-place contestant.
Alberto Fernández will assume the presidency on December 10.
What was this election about?
The vote was dominated by concerns over the economy. With nearly one in three people now living in poverty, voters backed the candidate they thought was best-placed to lead the country out of the crisis.
Mr Macri promised to achieve "zero poverty", but things actually worsened during his four-year rule. His supporters say he inherited a broken economy when he came to power and needed more time to sort it out.
Mr Fernández has vowed to play things safe financially.