Paolo Gentiloni was named Sunday as Italy's new prime minister following reformist leader Matteo Renzi's resignation in the wake of a crushing referendum defeat.
Gentiloni, who served as foreign minister under Renzi, was asked by President Sergio Mattarella to form a new centre-left government that will guide Italy to elections due by February 2018.
A close ally of the outgoing premier, Gentiloni now has to put together his own government team ahead of a parliamentary approval vote expected on Wednesday.
In a brief statement, Gentiloni said there was an "urgent need for a fully functioning government" to address a series of pressing international, economic and social issues.
Chief among those is a looming crisis in the troubled banking sector and ongoing relief efforts after a series of deadly earthquakes between August and October.
Mattarella turned to Gentiloni after opposition parties rebuffed overtures about a possible national unity government. The president rejected opposition demands for an immediate election.
"Not by choice but out of a sense of responsibility I will be forming a government based on the outgoing majority," Gentiloni said.
Renzi, who had been in power for two years and 10 months, resigned last week after voters overwhelmingly rejected a package of constitutional reforms on which he had staked his future.
The populist Five Star Movement, which has led calls for immediate elections, said it would boycott Wednesday's vote because the new government would have no legitimacy.
"This government is not even worthy of a vote against it," said Giulia Grillo, head of the Five Star group in the Senate.
Gentiloni, 62, is very close to Renzi and will be seen by the opposition as a puppet premier keeping the seat warm for former boss, who is planning a comeback at the next elections, whenever they are.
In a statement on his Facebook page, Renzi, 41, admitted it had been a wrench to leave office and vowed to pursue his reform agenda.
"It was painful to pack the cartons yesterday evening, I'm not ashamed to say: I'm not a robot," he wrote. "Only those who try to change things can help a country as beautiful and difficult as Italy."
Five Star, Italy's biggest opposition party, and the far-right Northern League are demanding a vote as early as possible.