Gentiloni was summoned for talks at the presidential palace on Sunday morning.
President Sergio Mattarella asked the 62-year-old to form a new government.
After consulting with around 40 political parties over the past three days, Mattarella pledged on Saturday to act quickly to give the country a fully-
Gentiloni promised to begin work on forming a new government as soon as possible.
“During the negotiations, we noted the reluctance of the opposition parties to share the responsibilities of the new government,” he told reporters.
“Therefore, we are not doing this by choice, but rather because we have the duty to do it. And so, we will proceed with the government and the current majority.”
Why is the position vacant?
Caretaker Prime Minister Matteo Renzi resigned last week after losing a referendum on constitutional reform.
His plans were voted down by 59% to 41%, prompting him to honour a pledge he had made to stand down.
What now for Gentiloni?
After formally receiving the mandate from Mattarella, the 62-year-old former journalist will begin consulting with political groups to form a government.
Renzi’s Democratic Party (PD) has a majority in both houses of parliament.
However, the PD itself is severely divided between Renzi backers, like Gentiloni, and opponents.
He will report back to Mattarella on his progress in rallying support.
If he cannot form a government, Mattarella could ask someone else to try.
If, however, Gentiloni is successful, a new government could be installed within days.
BREAKING: New Italian Premier-designate Paolo Gentiloni says he'll try to form Italy's new government as soon as possible.— The Associated Press (@AP) 11 dicembre 2016
All Italy’s major parties have called for elections as soon as possible.
However, before any vote can be held, the country needs a new electoral law to replace one that applies only to the lower house.
This could be declared illegitimate in January by Italy’s constitutional court.
The legislature is due to carry on until 2018.
However, early elections could be called at any time after parliament rewrites the electoral law.
BREAKING: Italian Prime Minister Renzi has resigned - statement from president's office pic.twitter.com/B8Zgx9k4fK— Reuters Top News (@Reuters) 7 dicembre 2016
The legislature is due to carry on until 2018, but early elections could be called at any time after parliament rewrites the electoral law.
A banking crisis?
Italy’s next prime minister will immediately face a crisis in the banking sector.
The country’s third-largest lender, Monte dei Paschi di Siena, may need state intervention to avoid collapse.
Did you know?
Italy has had 63 governments in the last 70 years.