Mille addressed thousands of supporters at his campaign headquarters in Buenos Aires after his landslide victory of more than 55 percent of the vote over centrist Economy Minister Sergio Massa, stressing that "this is a historic night for Argentina."
"The poor class model is over, and today we are adopting the model of freedom to once again become a global power. Today the way politics was practiced ends, and another method begins."
"We face enormous problems: inflation, recession, lack of real jobs, insecurity, poverty and misery. These are problems that will only be solved if we adopt the ideas of freedom again," he said, according to AFP.
Javier Milley, who has been calling for shock treatment for an economy exhausted by chronic inflation of 143 percent over one year, warned that "there is no room for gradualism, no room for apathy or half-measures."
He reached out to "all Argentines, political leaders and all those who want to join the new Argentina," but also warned of possible social resistance movements to his reforms.
"We know that there are people who will resist and want to maintain the system of privileges (that benefits some) but impoverishes the majority. I tell them: everything that is in the law is permissible, but not what is outside the law."
Milley will take over from center-left Peronist President Alberto Fernandez on December 10.
Admission of defeat
For his part, Argentine Economy Minister Sergio Massa admitted defeat in the run-off of the presidential election, which was held on Sunday, against rival Javier Milley.
Massa added from his campaign headquarters in Buenos Aires: "I called Javier Milley to congratulate him."
Preliminary official results showed Massa winning 45 percent of the vote.
Congratulations from Bolsonaro
Former Brazilian President Jair Bolsonaro on Sunday congratulated Argentina's president-elect, saying "hope is shining again" in the region.
Bolsonaro wrote on platform X: "Congratulations to the Argentine people on Javier Melé's victory. Hope is shining again in South America."
Brazil's right-wing former president added that he hoped "good winds will blow over the United States and Brazil" so that "honesty, progress and freedom can return."
Blinken and Trump congratulate
In Washington, the United States on Sunday congratulated Argentina's president-elect on his election victory, praising the "high turnout and peaceful conduct of the voting process."
U.S. Secretary of State Antony Blinken said in a statement that the election is "a testament to Argentina's electoral and democratic institutions," adding that the United States "looks forward to working with President-elect Milley and his government on shared priorities."
For his part, former US President Donald Trump on Sunday, congratulated Milley on his election as president of Argentina, saying through his social network Truth Social that he will work to "change" his country.
Addressing Milley, Trump wrote: "I'm so proud of you. You will change your country and make Argentina great again."