Lebanon's President Michel Suleiman has named Saad Hariri as the country's new prime minister, following parliamentary election earlier this month, BBC reported.
Mr Hariri's pro-Western alliance won 71 out of 128 seats in the vote, with the Hezbollah-led bloc taking the rest.
His choice as leader was confirmed when 86 MPs backed his nomination.
Mr Hariri, the son of assassinated former Prime Minister Rafik Hariri, must now form a cabinet from the country's polarised political factions.
The 39-year-old said he would seek to form a national unity government.
"In line with our commitment during the election campaign in favour of a national unity government in which the main parliamentary blocs are represented... we will begin consultations with all parliamentary blocs," he said.
Analysts have said any unity government will almost certainly include members of the militant movement Hezbollah or its supporters.
Once he has formed a cabinet, Mr Hariri will take over from his ally Fuad Siniora, who has held the post since 2005.
The turnout for the 7 June poll was 54% - the highest percentage among Lebanon's three million voters since the 1975-91 civil war.
The campaign was marred by mud-slinging and accusations that large numbers of expatriate Lebanese were flown home for free to cast votes.
But international observers said they were satisfied the poll was free and fair.
After years of Lebanon's domination by Syria, the pro-Western bloc swept to power in 2005 following the assassination of Rafik Hariri in a car bombing in Beirut.
Popular discontent after the bomb attack forced Syria to withdraw its troops amid accusations of its involvement in the killing. The government in Damascus has strongly denied the claims.