Kais Saied wins 73 percent of the votes, the electoral commission says. His opponent, Nabil Karoui, had already conceded defeat.
Kais Saied, a political outsider who wants to remake national politics won a landslide victory in Tunisia's presidential election which he hailed as a "new revolution."
Saied won 73 percent of the votes cast in Sunday's election, according to preliminary official results released by the electoral commission on Monday, and turnout was 55 percent. His opponent, Nabil Karoui, had already conceded defeat.
Saied's victory is a stinging rebuke for a governing elite that has failed to improve living standards or end corruption since the 2011 revolution in the North African country that introduced democracy and ushered in the "Arab Spring."
Saied, a 61-year-old retired law professor, wants to introduce an experimental form of direct democracy. But he has no political party of his own and faces big challenges including high inflation and unemployment.
"What I have done is a new revolution," Saied told a crowd of supporters gathered at his home in the Mnihla district on the outskirts of Tunis after his landslide victory became clear.
"I tell Tunisians that you have impressed the world."
'It will not be easy'
Large crowds of people waving Tunisian flags and chanting many of the old songs and slogans from the 2011 uprising filled the central Habib Bourguiba Street late on Sunday and celebrated into the early hours of Monday.
Olfa Radouan, a 53-year-old woman who brought her husband and two children to celebrate Saied's victory, said she understood that he would face big challenges.
"It will not be easy. He will face a complicated political situation, a very difficult economic situation, unstoppable social demands," she said.
Though exit polls had given Saied a huge lead soon after voting ended on Sunday, his opponent had left open the possibility that he might appeal against the result.
Karoui, a media mogul, was detained in August pending a verdict in his trial for money laundering and tax evasion –accusations which he denies – and was released only last Wednesday.
But Karoui conceded defeat and congratulated him several hours before the preliminary results were announced.