Benny Gantz's nomination marked the first time since 2008 that someone other than Netanyahu, has been asked by Israel's president to build a ruling coalition.
Former military chief Benny Gantz received an official mandate on Wednesday to try to form Israel's next government, but with no easy path to ending Prime Minister Benjamin Netanyahu's long hold on power.
After inconclusive elections in April and September, Gantz's nomination marked the first time since 2008 that someone other than Netanyahu, 70, has been asked by Israel's president to build a ruling coalition.
Gantz, head of the centrist Blue and White party, will have 28 days to complete the task assigned by President Reuven Rivlin in a televised ceremony.
Rivlin had first given Netanyahu the chance to form a government. But the prime minister, who leads the right-wing Likud party, announced on Monday he was abandoning the effort, opening the way for his strongest rival, Gantz, to be given the opportunity.
Replacing even a weakened Netanyahu, in office for the past decade and facing possible indictment over suspected corruption that he denies, could prove difficult without a significant shifting of political alliances. Gantz's failure could lead to a new election.
Gantz, who headed Israel's military from 2011 to 2015, currently has the endorsement of only 54 lawmakers — seven short of a parliamentary majority that neither the 60-year-old former general nor Netanyahu could secure in last month's vote and in the ballot in April.