Natalie Portman won the Oscar as best actress on Sunday for her role as an unhinged ballerina in the thriller "Black Swan," denying Annette Bening the golden statuette for the fourth time in her career.

The 29-year-old Israeli-American, considered the favorite after dominating other film awards shows leading up to the Oscars, was visibly overwhelmed as she dished out thanks in a trembling voice, and occasional stammer.

Portman trained five hours a day for six months to prepare for "Black Swan," a project she and director Darren Aronofsky first discussed about nine years ago. When they started shooting the film in 2009, it had yet to secure financing.

Her character, desperately insecure and possibly still a virgin, contends with professional jealousies and rivalries as she secures the dual lead roles in the ballet classic "Swan Lake". In the film, she grapples to separate truth from reality in a number of dream-like fantasy sequences.

A dazed Portman, whose roles have ranged from her breakout moment as an assassin-in-training orphan in "The Professional" to Queen Amidala in George Lucas' "Star Wars" prequels, drew some parallels with her onscreen persona.

"It feels very, very dream-like right now," said the pregnant Portman, clad in a flowing aubergine Rodarte that accommodated her growing bump. "I don't really remember anything that just happened just now. But the baby was definitely kicking a lot during the song portion of the show."

CRITICAL HIT

"Black Swan" was a commercial and critical hit, with worldwide ticket sales of more than $200 million. As a bonus, Portman last year announced she was pregnant and would marry the baby's father, a dancer she met on the "Black Swan" set.

Her film raised eyebrows, and drew considerable media hype for an explicit lesbian sex scene between Portman and co-star Mila Kunis.

"It's only possible to give yourself so, so freely when you absolutely 100-percent trust the person you are working with as your director," Portman said.

The actress faced down some formidable competition for the Academy Award: Bening for "The Kids Are All Right," Oscar-winner Kidman for "Rabbit Hole," newcomer Jennifer Lawrence for "Winter's Bone" and Michelle Williams for "Blue Valentine."

Portman previously received an Oscar nomination for her supporting role in the 2004 film "Closer."

Born in Jerusalem, she moved to the United States as a youngster and made her feature film debut in 1994 playing a 12-year-old girl who ends up in the care of the hired killer who assassinated her parents in "The Professional."

Portman next appears in studio tent-pole "Thor", about the mythological Norse God and super-hero, and also appears alongside Oscar co-host and nominee James Franco in period comedy "Your Highness".

But for now at least, having snagged the industry's highest honor, she longs for some peace and quiet.

"The next dream I have in terms of a very short-term future is staying in bed and not having to do my makeup or hair, and for my child just to be happy and healthy," she said.