Although the powers of the elected president are limited by those of unelected Supreme Leader Ayatollah Ali Khamenei who outranks him, the scale of Mr Rouhani's victory gives the pro-reform camp a strong mandate.
The nuclear agreement Mr Rouhani's government reached with global powers in 2015, under which most international sanctions have been lifted in return for Iran curbing its nuclear programme, is now likely to remain safe.
However, Mr Rouhani stills faces the same restrictions on his ability to transform Iran that prevented him from delivering substantial social change in his first term and thwarted reform efforts by one of his predecessors, Mohammad Khatami.
Voters were determined to block the rise of Ebrahim Raisi Image: Voters were determined to block the rise of Ebrahim Raisi The re-elected President will also face the challenge of navigating a tricky relationship with Donald Trump who has dubbed the nuclear agreement signed by former US President Barack Obama as "one of the worst deals ever signed".
He said: "During President Rouhani's first term we made good progress on improving UK-Iran relations, including an upgrade in diplomatic relations, and I welcome his continued commitment to the nuclear deal Iran signed up to in 2015.
Source: Sky News