Iran's tenth presidential election was held on 12 June 2009. Iran's official news agency announced that with two-thirds of the votes counted, Ahmadinejad had won the election with 63% of the votes cast and that Mir-Hossein Mousavi had received 34% of the votes cast. There were large irregularities in the results and people were surprised by them, which resulted in protests gathering millions of Iranians in every Iranian city and around the world.

Clashes broke out between police and groups protesting the election results from early morning on Saturday onward. Initially, the protests were largely peaceful. Despite the relatively peaceful nature of the protests, the Police and the Basij (a paramilitary group) suppressed them by using batons, pepper spray, sticks and, in some cases, firearms.

On June 15, Tehran and other cities have seen the largest street protests and rioting since the 1979 Iranian Revolution.

The Iranian government has disputed these allegations, and confirmed the deaths of 36 people during the protests, while unconfirmed reports by supporters of Green Movement allege that there have been 72 deaths (twice as many) in the three months following the disputed election, with a possibly higher number, since relatives of the deceased are forced to sign documents claiming they had died of heart attack or meningitis.