Australian Nicole Kidman burst into tears during her acceptance speech after winning today's best actress Academy Award.

"Russell Crowe said don't cry if you get up there and now I'm crying," Kidman told the 3,300 guests sitting in Hollywood's Kodak Theatre.

Kidman was shocked when last year's best actor winner, Denzel Washington, announced her name.

Kidman hugged her mother, Janelle, who was sitting next to her, while her father Antony, sitting behind her, lent over the seat and gave his daughter a kiss on the cheek.

Kidman's daughter, Isabella, was also sitting behind her. The actress gave the 10-year-old, who is seldom in the public eye, a kiss.

"I am standing here in front of my mother and my daughter," Kidman, who was fighting back tears, said in her speech.

"My whole life I wanted to make my mother proud ... and my daughter proud as well."

Kidman was the favourite for the best actress Oscar for her role in Hours, The (2002), but many thought Chicago's Renée Zellweger would win the award.

Kidman was nominated last year for Moulin Rouge (2001) but Halle Berry took the prize for Monster's Ball (2001).

There was speculation Kidman would skip today's awards because of the war in Iraq but she said it was important she attend.

"I do have to say 'Why do you come to the Academy Awards when the world is in such turmoil?'" Kidman pondered.

"Because art is important, because you believe in what you do and you honour that and it's a tradition that needs to be upheld."

The news was not as good for Australia's four other nominees.

Dion Beebe (cinematography for Chicago), Ben Snow (special effects for Star Wars Episode II: Attack of the Clones) and Steven Pasvolsky and Joe Weatherstone for their short film Inja all went home from the awards empty handed.

Kidman's win, the first by an Australian actress, crowns an amazing two years - a period in which she overcame the personal trauma of the break-up with husband Tom Cruise and a miscarriage to produce a body of quality and diverse work unparalleled by any other in her profession.

First there was the musical Moulin Rouge, for which she won an Oscar nomination, then she played an earnest young mother in the spooky thriller The Others, before becoming a Russian mail-order bride in last year's Birthday Girl.

But the increasingly demanding roles were just a build-up to the redhead's greatest dramatic challenge: playing the brilliant but manic depressive Virginia Woolf in Stephen Daldry's complex literary drama The Hours.

The Oscar caps her transformation from Hollywood wife to A-list star and top dramatic actress.

For Kidman, 35, it is the ultimate accolade and puts her firmly in the realm of Hollywood royalty in her own right.

At first she baulked at the role of the suicidal and dowdy Woolf, whose moments of desperation, stillness and mania she reflected in the film.

"I read the script and I couldn't believe they wanted me for Virginia. I thought there was no way I would be able to pull this off," she said.

But she threw herself into the role and immersed herself in the life and work of the author and said she tapped her loneliness following her divorce to play the part.

But while the tabloids have fixated on the huge prosthetic nose she donned to play Woolf, an accessory that along with dark hair rendered her almost unrecognisable, critics have hailed her wrenching performance.

AAP

Source: Press Release