Tunisians celebrate populist Kais Saied's presidential election victory
Saied's campaign slogan was "The People Want", which echoed the chants of the 2011 revolution which has brought a tentative democracy to the North African country.
His win attracted thousands to Tunis' main thoroughfare show their support with celebrations continuing until the early hours of Monday.
Revellers praised Saied for embodying the spirit of the revolution, waving national flags, setting off fireworks and honking car horns in a show of celebration.
Read more: Kais Saied: "Robocop" newcomer poised to be Tunisia's next president
The chants echoed Saied's policy positions, including those that denounced Egyptian President Abdel Fattah al-Sisi - currently embroiled in a corruption scandal - and those in support of Palestine, a cause Saied has vowed to support by rejecting normalisation with Israel.
Many regard the president-elect as a populist, who ran a small, grassroots campaign that won support from those disenchanted by mainstream parties.
The moderate Islamist-inspired Ennahda party, who won the legislative elections, endorsed Saied for president in September.
Despite voicing a conservative stance on social and religious issues similar to Islamist parties, Saied has shunned the Islamist label.
Saied rejects overhauling Tunisia's inheritance law - which remains based on Islamic law, meaning that women inherit half of their male siblings' part.
Tunisia is a semi-presidential republic, which grants the president power over the armed forces, foreign policy and national security.
The president shares the executive with the prime minister, who is appointed by parliament.
Upon the release of the exit polls on Sunday, the law professor-turned-politician thanked the "young people for turning a new page" in the country's history.
"We will try to build a new Tunisia," he told a gathering of supporters, his family and the press after state media announced his landslide election victory. "Young people led this campaign, and I am responsible for them."
In a contest - which reflected Tunisia's shifting post-revolution political landscape - Saied scooped almost 77 percent of the vote, according to Wataniya television.
Some 90 percent of voters aged 18 to 25 voted for Saied, according to polling institute Sigma, while just 49 percent of people above 60 chose him over his rival, business tycoon and media magnate Nabil Karoui.
The official results are expected Monday.
"I will carry the message" of the 2011 Arab Spring revolution that ousted dictator Zine El Abidine Ben Ali, Saied said.
"The law will be applied to all, and first and foremost to me," he said.
"Everyone made their choice, in complete freedom. Our project is founded on freedom. The era of submission is over. We have just entered a new era in history," he said.
"The state will be built on a foundation of trust. Trust between the leader and the people, and in a framework of respect for the rules," he added.
Agencies contributed to this report.