Moderate cleric Hassan Rouhani has called his defeat of conservative hardliners a victory of moderation over extremism and pledged a new tone of respect in international affairs.
Thousands of jubilant Iranians poured onto the streets in celebration of the victory on Saturday, chanting: "Long live reform! Long live Rouhani!", according to witnesses at the scene.
"Ahmadi, bye bye!" they added in reference to President Mahmoud Ahmadinejad - who was legally barred from seeking a third consecutive term.
Rouhani will take up the presidency, the highest elected office in Iran's hybrid clerical-republican system, in August.
"This victory is a victory of wisdom, a victory of moderation, a victory of growth and awareness and a victory of commitment over extremism and ill-temper," Rouhani told state television, promising to work for all Iranians, including the hardline so-called "Principlists" whom he defeated at the poll.
"I warmly shake the hands of all moderates, reformists and Principlists," he said.
Matters of national security remain the domain of Supreme Leader Ayatollah Ali Khamenei, but the president runs the economy and wields broad influence in decision-making in other spheres.
New tone
Rouhani seemed to strike a new tone in the way he talked about Iran's relations with the rest of the world.
He said there was a new chance "in the international arena" for "those who truly respect democracy and co-operation and free negotiation".
Though an establishment figure, Rouhani was known for his nuanced, conciliatory approach when he was Iran's chief nuclear negotiator.
Rouhani's nearest rival was conservative Tehran Mayor Mohammad Baqer Ghalibaf, a long way behind with less than 16 percent. Other hardline candidates close to Khamenei, including current nuclear negotiator Saeed Jalili, scored even lower.
Iran's rial strengthened about four percent against the US dollar on Saturday after partial vote tallies pointed to an easy Rouhani victory, web sites tracking the currency said.
Washington said it stood ready to engage with Iran to reach a "diplomatic solution" over its nuclear program, which the West suspects is intended to produce nuclear weapons - something Iran denies.
PHOTO CAPTION
Iranian Presidential candidate Hasan Rowhani, a former Iranian nuclear negotiator, delivers a speech, in his campaign rally at the northwestern city of Tabriz, Iran, Monday, June 10, 2013.
Al-Jazeera