After avoiding a run-off with a 57% outright victory over his main rival, Mr Rouhani said he respected his opponents' right to criticise him. Mr Rouhani, 68, supports the landmark deal to curb Iran's nuclear programme. The decisive victory gives him a strong mandate to seek reforms and revive the country's ailing economy, analysts say. "The Iranian nation has chosen the path of interaction with the world, a path which is distant from extremism and violence," Mr Rouhani said in his first speech after the victory, broadcast on state television. "The election is now over. I am the president of the nation and need assistance from every single Iranian, even those who oppose me and my policies." Mr Rouhani also thanked former reformist President Mohammad Khatami, apparently defying a media ban on citing the ex-leader's name.
What were the results?
Turnout in the election was unexpectedly high, at about 70%. And this is thought to have helped Mr Rouhani, who received close to 23 million votes out of the 40 million that were cast. His main challenger, former prosecutor Ebrahim Raisi received 38.5%, or 15.7 million votes, which was not enough to take the election to a second round. On Twitter, Iran's Supreme Leader, Ayatollah Ali Khamenei, said the election had showed the "increasing progress" of the "Iranian nation". Mr Khamenei said Iran would demonstrate "national dignity" and "wisdom" in relations with other countries. But he did not congratulate Mr Rouhani for his victory. There were celebrations in the capital, Tehran, with young people singing and dancing in the central Vali Asr Square, despite efforts by police to move them, the AFP news agency reported.
What are the challenges?
The economy seems to be the number one issue. Average Iranians say they do not feel the economic benefits after international sanctions were lifted as a result of a nuclear deal signed between Iran, the US and other countries in 2015. While oil exports have rebounded and inflation is back at single-digits, unemployment remains high, especially among young people. Mr Rouhani also promised a moderate vision and an outward-looking Iran and, at rallies, openly attacked the conservative-dominated judiciary and security services. But Mr Rouhani's own powers are limited by those of Ayatollah Khamenei, who has the last say on many crucial and strategic issues.
Mr Rouhani was re-elected with 57% of the vote
Another challenge, experts say, comes from abroad, and relations with the new US government under President Donald Trump. Mr Trump opposes the nuclear deal which eased sanctions on the Middle Eastern country, describing it as the "worst deal ever". But, despite the objections, the White House renewed the agreement earlier this week.
'Revenge against hardliners': By Kasra Naji, BBC Persian