The nomination of Hariri, long aligned with Western and Gulf states, follows weeks of political wrangling that has delayed a deal on a new government. He was backed by his own Future Movement, the Shi'ite Amal party, Druze politician Walid Jumblatt's party and other small blocs.
The heavily armed Shi'ite group Hezbollah, which took part in Hariri's last coalition cabinet, did not nominate anyone but said it would seek "to maintain the positive climate." Together with its allies, including Amal and Aoun's party, they hold a majority in parliament.
Lebanon's two main Christian blocs did not nominate Hariri.