The Lord of the Rings: The Return of the King also took best director for Peter Jackson, who spent seven years making the trilogy, tied the record for Oscar wins set by 1997's Titanic and 1959's Ben Hur.
"I'm so honoured and that Academy and its members have seen past the trolls and the wizards and the hobbits and are recognising fantasy this year," Jackson, 42, said on Monday as he received his Oscar as a producer of the best picture of 2003.
"Fantasy is an 'F' word that hopefully the five second delay won't do anything with," he said quipping about the first ever delay slapped on the Oscars US telecast to cut out and obscenities.
Best leading roles
In a night in which all the predicted favourites won, Charlize
Theron snatched the best actress Oscar for her role as a serial killer and prostitute in Monster, and former Hollywood bad boy Sean Penn was forgiven by Hollywood, winning best actor for Clint Eastwood's drama Mystic River.
And fellow front-runners Renee Zellweger scooped the statuette for best supporting actress for Civil War drama Cold Mountain and Tim Robbins won best supporting actor for his role as a bereaved father in Mystic River.
The final Rings spectacular picked up Oscars for best visual
effects, best costume design for the double-nominated New Zealander Ngila Dixon, best original song and best original musical score for Howard Shore.
It also won for film editing and for best art direction, best
sound mixing and best makeup.
"There is nobody left to thank in New Zealand," joked Oscar
host Billy Crystal after the umpteenth New Zealander linked to the spectacular went up to claim a statuette.
The outspoken Penn, who has long spurned Hollywood's traditions, won the Academy Award with his fourth nomination, following nods for Dead Man Walking, Sweet and Lowdown and I Am Sam.
Oscar winner Sean Penn has
made an anti-Iraq war statement
He accepted the award with a barb against the US administration over the Iraq war, in front of an audience of up to a billion television viewers watching the 76th annual Academy Awards show.
"If there is one thing that actors know - apart from the fact that there were no WMDs," he said in a nod to his fellow nominees "is that there are no bests in acting."
An emotional former South African farm girl Theron, the country's first ever Oscar winner, was overcome.
"This has been such an incredible year. I can't believe this," she said as she received the award, thanking her mother for having "sacrificed so much for me to make my dreams come true."
Best supporting roles
Zellweger won for her role as a spirited country girl in Anthony Minghella's Civil War drama Cold Mountain, while the outspoken Robbins won his first Oscar and Hollywood's embrace for his supporting role as a man who was abused during childhood in Clint Eastwood's drama Mystic River.
"I am so honoured and that Academy and its members have seen past the trolls and the wizards and the hobbits and are recognising fantasy this year."
Lord of the Rings director
Green party activist Robbins, who caused a furore along with his partner Susan Sarandon in their opposition to the US-led war in Iraq last year, said backstage he was surprised Hollywood had finally blessed him.
"I am sure a lot of people voted for me that don't agree with my politics," he said.
Best foreign film
Canada's The Barbarian Invasions, written and directed by Denys Arcand won best foreign language film.
South African Charlize Theron has
snatched the best actress oscar
Billy Crystal, doing his eighth turn on cinema's biggest stage, mounted a hilarious musical spoof of this year's Oscar hopeful movies and stars.
But there were also poignant moments to the show attended by around 3000 Hollywood stars and moguls all fitted out in their finest.
Celebrated writer and director Blake Edwards, 81, received an honorary Oscar for his 50-year lifetime of work that includes Breakfast at Tiffany's and the Pink Panther movies.
And Julia Roberts presented a moving tribute to four-time best actress Oscar winner Katharine Hepburn who died at 96 in June. There also were homages to Bob Hope and Gregory Peck, who both died last year.