But when the business-friendly mayor of Buenos Aires takes office on 10 December, he will inherit a country with around 30 per cent inflation, near-zero economic growth and entrenched government social spending that private economists warn is not sustainable.
He also lacks majorities in either chamber of congress to pass his deep reforms.
“Macri will begin his mandate in a difficult political position,” Daniel Kerner from the Eurasia Group, a political risk consultancy, wrote. “He will have to make difficult economic adjustments and face serious political constraints.”
With 98 per cent of the vote counted, Mr Macri, 56, had 51.5 per cent support compared with 48.5 per cent for ruling party candidate Daniel Scioli, President Cristina Fernandez’s handpicked successor.
Mr Scioli, governor of the vast Buenos Aires province, conceded defeat and Mr Macri claimed victory.
“Today is a historic day,” said Mr Macri, addressing thousands of cheering supporters as horns blared across Buenos Aires. “It’s the change of an era.”
The 12-year era he hopes to end is that of Ms Fernandez and her late husband and predecessor Nestor Kirchner who rewrote Argentina’s social contract and dominated the nation’s political scene with a mix of patronage, charisma and withering attacks on opponents.
Ms Fernandez battled international creditors, had strained relations with Washington and allied her country with Venezuelan president Hugo Chavez and his successor Nicolas Maduro.
During the election campaign, Mr Macri vowed he would listen more and talk less than Ms Fernandez.
He said his presidency would not be about “revenge” or “settling scores”, but rather helping the country progress.
“I feel so happy because today we put an end to the [political] mafia” said Felisa Sanchez, a Macri supporter waving an Argentine flag.
“They claimed to be Robin Hood helping the poor with social welfare plans when the poor are really helped with jobs and education.”
But fulfilling his campaign promises may prove difficult.
Mr Macri has pledged to lift unpopular controls on the purchase of US dollars and thus eliminate a booming black market for currency exchange. Doing that would probably lead to a sharp devaluation of the Argentine peso.