Conservative academic Kais Saied on Sunday won a landslide victory in Tunisia's presidential runoff, sweeping aside his rival, media magnate Nabil Karoui, state television Wataniya said.
It said he scooped almost 77% of the vote, compared to 23% for Karoui.
News of the victory triggered celebrations at the retired law professor's election campaign offices in central Tunis, as fireworks were set off outside and supporters honked car horns.
The turnout stood at 38.2%, three hours before the voting ended, the electoral commission said at a press conference, adding that the participation was higher than that in Sunday's legislative elections.
About 7.2mn people were registered to vote, with more than 4,500 polling stations across the country.
It has been less than a decade since Tunisia, the origin of the 2010-11 Arab Spring revolts, toppled its long-time autocratic government in favour of democratic elections.
Social unrest, militant attacks and an economic slowdown have afflicted the country on its fledgling democratic path. The unemployment rate is about 15%.
Media tycoon Nabil Karoui, 56, has been tarnished by corruption allegations. He was released from jail on Wednesday after spending more than a month in custody on money laundering and tax evasion charges.
Karoui, who has not been convicted, presents himself as an advocate of Tunisia's poor and marginalised as the head of the recently founded centre-left Heart of Tunisia party.
Law professor Saied, 61, is an independent with no political experience. He has pledged to fight corruption and support decentralisation.
Both topped the election's first round on September 15, defeating contenders from mainstream political parties.
The two political outsiders' electioneering has been very unusual, with Karoui having been released only four days before the final round, and Saied having kept a low profile since the first round and later announcing that he would stop campaigning for "ethical reasons" related to the lack of equal opportunity between the two candidates.