Centre-right opposition candidate Mauricio Macri has won the presidential election run-off election in Argentina, according to exit polls.
Mr Macri went up against Daniel Scioli, the governor of Buenos Aires province, in Sunday's vote.
Neither candidate garnered enough of the vote in the first round to win outright, forcing a run-off.
Mr Scioli was marginally ahead in the first round, with 36.7 percent to 34.5 percent, but has lost ground to his rival since.
The son of one of Argentina's richest men, Mr Macri had a long career in business before entering politics.
He leads the conservative Cambiemos (Let's Change) coalition.
A close ally of current President Cristina Fernandez de Kirchner, Mr Scioli had been expected to win by a greater margin in October.
Under Argentinian law, a presidential candidate needs 45 percent of the vote or a minimum of 40 percent with a 10-point lead over the nearest rival to win outright.