Gentiloni told journalists Sunday that he had accepted Italian President Sergio Mattarella's request to form a new government after meeting with the president at the Palace of Quirinale. If successful, he will need Parliament's approval to officially assume the office of prime minister.
He would replace caretaker Prime Minister Matteo Renzi, who officially resigned Wednesday after a crushing defeat in a referendum on constitutional changes he proposed.
After the one-hour meeting with Mattarella, Gentiloni said he would continue in the path of the previous government and make sure that a draft electoral law is approved.
"I am ... conscious of the urgency to give to Italy a full-power government in order to reassure our citizens and be able to face, with the utmost commitment and determination, priorities that are international, economic and social, starting from the reconstruction of the areas hit by the earthquake," Gentiloni said at the palace.
The electoral law was passed in July in an effort to make the passage of laws quicker and easier. It gave parties in the lower house of Parliament extra seats if they won more than 40% of the vote.
But its validity has come into question as proposed constitutional changes, including the reduction of seats in the upper house, were rejected in last week's referendum.
Almost 60% of voters last week rejected Renzi's proposals for constitutional change in what was seen as a referendum on the prime minister's leadership and a litmus test for the rise of populism in the country.
Italian media were quick to paint Gentiloni as a Renzi ally. The online edition of La Stampa described the prime minister-designate as among the "super faithful to Renzi" but the "polar opposite" in terms of style and character.
Gentiloni, 62, is a former journalist who became spokesman for the Mayor of Rome in 1993 and was elected a member of Parliament in 2001.
He served as Minister for Communications from 2006 to 2008 in Prime Minister Prodi's government. Gentiloni was one of the 45 members of the national founding committee of the Democratic Party in 2007.
Who's the populist?
Renzi's intention was to change the 1948 constitution by reducing the the 315 seats in the Senato to 100, making it more of a consultative assembly.
His referendum gave way to accusations of populism in both the "Yes" and "No" camps.
The "No" campaign was spearheaded by the anti-establishment Five Star Movement party led by Beppe Grillo, who has been accused of pandering to populist sentiment.
If Gantiloni cannot form a new government, a snap election could be called, in which the Five Star Movement would make substantial gains, analysts have said.
Grillo, an entertainer-turned-politican, made a name for himself on Italian TV in the 1970s and 1980s. He capitalized on his show-business bravado to promote an anti-establishment movement spanning both the political left and right.
Foreign observers fear that if Grillo comes to power in an early election, he'll call a referendum to scrap the euro, go back to the Italian lira, and perhaps even follow Britain out of the European Union.
But Renzi was also accused of running a populist campaign, touting the reforms as a way to have "less politicians." Renzi said in an interview before last week's referendum that a "yes" vote was the true "anti-establishment choice."