Reyhaneh Jabbari walked to the gallows at dawn on Saturday in Tehran's Evin prison after failing to secure a reprieve from the murder victim's relatives within the 10-day deadline set by sharia law in force since 1979 Islamic Revolution.
The death sentence sparked international condemnation, prompting the government of President Hassan Rouhani, who won election last year partly on promises of liberal reform, to intervene to get it commuted.
Justice Minister Mostafa Pour-Mohammadi in early October said a "good ending" was in sight but official media reported later that the slain man's family could not be persuaded to approve leniency for Jabbari.
Jabbari was sentenced to death in accordance with Koranic "qisas", or eye for an eye, law after being found guilty of stabbing dead an older man with a kitchen knife in 2007.
She had pleaded self-defence but failed to sway judges at various stages of appeal and had been kept in prison since her arrest.
Her last chance of reprieve lay with Supreme leader Ayatollah Ali Khamenei, whose powers transcend all state mandates, but he never mentioned the case and has only rarely intervened in court cases regardless of political considerations.
Immediately after the execution, the Tehran state prosecutor's office issued a statement that appeared aimed at countering sympathy for Jabbari.
"Jabbari had repeatedly confessed to premeditated murder, then tried to divert the case from its course by inventing the rape charge," said the statement carried by IRNA.
"But all her efforts to feign innocence were proven false in various phases of prosecution. Evidence was firm. She had informed a friend through text message of her intention to kill. It was ascertained that she had purchased the murder weapon, a kitchen knife, two days before committing murder."
The hanging comes at an inopportune time for Rouhani, who has been treading a precarious path to rapprochement with the West after decades of mutual hostility.
Rouhani has come under fire from secular Iranians, his main political constituency, over a spate of acid attacks on young women deemed by their attackers to have insufficiently covered their hair in accordance with sharia. Many Iranians believe the attacks have been provoked by Islamist hardliners in a continuing campaign to thwart the political and social reforms pledged by Rouhani during his electoral campaign.
The US Saturday condemned the move. "We condemn this morning's execution in Iran of Reyhaneh Jabbari," said the statement by State Department spokeswoman Jen Psaki, who said there were "serious concerns with fairness of the trial and circumstances surrounding this case."