Ahmadinejad's victory is considered a major blow to Iran's reformist camp, who have lost their last stronghold.
In his first public reaction to his shock victory, Iran's president-elect said that the Islamic Republic's "enemies" had been "checkmated."
Ahmadinejad also called upon Iranians to forget their rivalries and work together "to make a great society."
"I definitely feel very honored that people have trusted me and have been kind to me, it's a great honor for me but the honor of serving people is even bigger -- whether it is in the municipality, in the presidency or sweeping streets for this nation, it does not make any difference," Ahmadinejad said.
The Tehran mayor, a former member of Iran's Revolutionary Guard, was a relatively unknown figure in Iran until he reached the runoff last week.
But yesterday, he swept to a resounding victory against his rival, the more moderate Ayatollah Hashemi-Rafsanjani.
Ahmadinejad is said to be a strict follower of conservative Islamic principles who has promised to improve the lot of the poor. He has also said that he will distribute oil revenues. Poor provinces are reported to have voted massively for Ahmadinejad.
Dr. Sadegh Zibakalam, a professor of political science at Tehran University, told Radio Farda that many people voted for Ahmadinejad hoping that his presidency would bring social justice and narrow the gap between the rich and the poor.
Zibakalam says Ahmadinejad also picked up votes from conservatives. "The conservatives as a social movement have a relatively significant social base that includes the society's more religious groups, the families of the martyrs, organs such as the Basij, the Revolutionary Guard, their supporters, villagers," he said.
Zibakalam believes that other factors such as the pre-election campaign also contributed to Ahmadinejad's victory.
"Another part of the votes were the results of the negative campaign against Mr Hashemi-Rafsanjani during the elections or before by the radical reformists who said all the country's problems were created as a result of his actions. I think the organized [campaign] of the conservatives against Mr. Rafsanjani was effective. But for sure, part of the votes were from people who believed that their bad living conditions, their poverty are due to the policies by Mr. Rafsanjani that were continued during the eight-year presidency of Mr. [Mohammad] Khatami," Zibakalam said.
Ahmadinejad will succeed reformist President Mohammad Khatami, who constitutionally could not seek a third term.
His victory gives hard-liners control over every elected or unelected state institution in Iran.
So it's a major blow to Iran's reformist camp. They are worried Ahmadinejad might roll back reforms, and had called on supporters to vote for Hashemi-Rafsanjani to prevent the Tehran mayor from winning.
Farah Karimi is an Iranian-born member of the Dutch parliament. In an interview with RFE/RL, Karimi expressed concern that an Ahmadinejad's victory could lead to a deterioration of the human rights situation in Iran.
"I think his election is an indication that in the future, we could see some set-back in the relative social freedoms that were achieved, and that human rights will probably be under great pressure, as well as freedom of expression, because [Ahmadinejad] himself had announced in his campaign that democracy and freedom is not his main issue," Karimi told RFE/RL.
Washington last night condemned the Iranian elections as flawed and said that Iran is "out of step" with regional trends toward democracy.
Some observers believe that Ahmadinejad's victory could complicate any prospects of improvement of ties between Tehran and Washington.
Ahmadinejad said before the 24 June vote that ties with the U.S. would not solve people's problems.
They say that it could also put Iran on a collision course with the EU countries that have been negotiating with Iran over its nuclear fuel program.
Today Britain criticized "serious deficiencies" in Iran's elections and urged the next president to address international concerns about the country's nuclear program. There were similar calls from France and Japan.
Ahmadineajd has in the past criticized Iran's nuclear negotiators as being "terrified" and bowing to European pressure at the negotiating table.
Farah Karimi the Dutch parliamentarian believes that Ahmadinejad's victory could also complicate the Iran-EU nuclear talks.
"If his message is that Iran will not be ready under any conditions to respond to EU demands that Tehran abandon its uranium enrichment program, and if they enter the negotiations with a tough message, then probably [Iran's nuclear case] will be very quickly referred to the UN Security Council," Karimi said.
Iran's Supreme Leader Ayatollah Ali Khamenei said today that the election was "a humiliation" for the U.S. He called on Iranians to put aside their differences.
(Radio Farda correspondent Mina Baharmast contributed to this report )
See also:
A New Generation And The Drift To The Right
Ethnicity And Regional Interests Play Out In Vote
For RFE/RL's full coverage of Iran's elections, see "Iran Votes 2005"