Mauricio Macri won the historic ballotage and is the first head of state from 1916 which belongs neither to the Peronist nor to the Radical Party.
Mr Macri is expected to reverse the national policies of Ms Fernández and her husband Néstor Kirchner (who preceded her as president and died in 2010).
The new president will also improve relations with foreign creditors and with the United States.
After receiving a ceremonial scepter and sash at the Casa Rosada, the country’s presidential palace, Mr. Macri joined his wife, Juliana Awada, 41, in waving to supporters from a balcony. Reprising a frequent feature of his campaign, Mr. Macri danced a solo performance before meeting with foreign dignitaries.
Mr. Macri has vowed to cut inflation to a single digit within two years, though advisers are trying to find way to do so without weakening the economy.