In an open letter published Monday, more than 80 actors, artists, musicians, academics and politicians said that "Sakineh Mohammadi Ashtiani has suffered enough."
Signatories include actor Colin Firth, artist Damien Hirst, Nobel literature laureates Wole Soyinka and V.S. Naipaul, British opposition leader Ed Miliband and former French foreign minister Bernard Kouchner. They say Ashtiani has already spent five years in prison and received 99 lashes.
They called on Iran's Supreme Leader Ayatollah Ali Khamenei and President Mahmoud Ahmadinejad to release her along with her son and lawyer, who are also imprisoned.
The letter was published on the front page of The Times of London newspaper.
Ashtiani, 43, was convicted in 2006 of having an "illicit relationship" with two men after the murder of her husband the year before and was sentenced at that time to 99 lashes. She was later convicted of adultery and sentenced to be stoned.
Iran also says she has confessed to complicity in her husband's murder.
After coming under intense demands from Western politicians and rights groups to free Ashtiani, Iran put her stoning sentence for adultery on hold in July for review by the country's supreme court.
Stoning was widely imposed in the years following the 1979 Islamic revolution, and even though Iran's judiciary still regularly hands down such sentences, they are often converted to other punishments. The last known stoning was carried out in 2007.