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"There are eight great films that have as much right to be up here as we do," said "Argo" producer and director Ben Affleck.
The not-so-unexpected win for "Argo" was announced in one of the biggest surprises in the history of Oscar telecasts as first lady Michelle Obama made an unprecedented appearance from the White House to declare the top winner of the evening.
It was the first time since "Driving Miss Daisy" in 1990 that a film won the top prize at the Oscars without its director also being nominated.
Michelle Obama announces Best Picture winner (Photo: AFP)
Daniel Day-Lewis made Oscar history and won a long standing ovation on becoming the first man to win three Best Actor Oscars. He collected the golden statuette for his intense performance as US President Abraham Lincoln in "Lincoln."
"I really don't know how any of this happened," said Day-Lewis, who has dual Anglo-Irish citizenship.
Jennifer Lawrence was named Best Actress for playing a feisty young widow in comedy "Silver Linings Playbook", tripping up on her dress while approaching the stage. She beat Jessica Chastain and France's Emmanuelle Riva, 86, in one of the closest Oscar contests this year.
Taiwanese director Lee beat front-runner Steven Spielberg in the directing race, in a controversial year that saw four of Hollywood's leading names omitted from the Academy Award directing shortlist.
Spielberg's account of President Lincoln's battle to abolish slavery and end the US civil war went into Sunday's three-hour plus ceremony with a leading 12 nominations. But it ended up winning just two.
Best Director winner, Ang Lee (Photo: Reuters)
"Argo" also won best film editing and best adapted screenplay for its gripping and often comedic tale of the CIA mission to rescue six US diplomats from Tehran shortly after the Islamic Revolution.
In other contests, Anne Hathaway won her first Oscar and harrowing Austrian film "Amour" was voted Best Foreign Language Film.
Hathaway, who starved herself and chopped off her long brown locks to play tragic heroine Fantine in "Les Miserables," was considered the overwhelming favorite for supporting role in the screen version of the popular stage musical.
"It came true," she said, looking at the golden statuette.
"Here's hoping that some day in the not too distant future the misfortunes of Fantine will only be found in stories and not in real life," Hathaway added.
Anne Hathaway wins Best Supporting Actress (Photo: AFP)
"Amour," the heart-wrenching tale of an elderly couple coping with the wife's debilitating stroke, gave Austria the Best Foreign Language film after it had dominated awards shows in Europe and the United States for months.
Another Austrian, Christoph Waltz, was the surprise winner of the closest contest going into the ceremony. He took Best Supporting Actor honors for his turn as an eccentric dentist turned bounty hunter in Quentin Tarantino's slavery revenge fantasy "Django Unchained."
It was Waltz's second Oscar, after winning for the Tarantino movie "Inglourious Basterds" in 2010.
A jubilant Tarantino also won the Oscar for Best Original Screenplay, and credited the actors who brought the characters in all his films to life. "And boy this time, did I do it!," he said.
"Brave," the Pixar movie about a feisty Scottish princess, took home the golden statuette for Best Animated Feature.
The Oscar winners were chosen in secret ballots by some 5,800 members of the Academy of Motion Picture Arts and Sciences.