"Argo" bested eight rivals for the top prize: "Amour," "Beasts of the Southern Wild," "Django Unchained," "Les Miserables," "Life of Pi," "Lincoln," "Silver Linings Playbook," and "Zero Dark Thirty."

On Nicholson's cue, Obama -- in a glittering silvery gown as stunning as any worn by the stars inside the Dolby Theatre in Hollywood -- opened the envelope at the White House and declared "Argo" the winner.

"I want to thank Canada. I want to thank our friends in Iran, who live under terrible circumstances," said Affleck, a co-producer of the film, speaking at top speed in the very last minutes of the live prime-time Oscar broadcast.

"Argo" recounts how a group of US diplomats who took refuge in the Canadian embassy in Tehran during the Iran hostage crisis were spirited out of the Islamic republic as members of a bogus movie crew.