'Birdman' has scooped best film at the Oscars, with British actor Eddie Redmayne winning best actor for 'The Theory Of Everything.'
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Mexican director Alejandro Inarritu also won best director for 'Birdman', which featured a career-resurrecting performance by Michael Keaton.
It also won for cinematography and original screenplay.
Redmayne's memorable portrayal of Hawking saw off competition from Benedict Cumberbatch, Bradley Cooper, Michael Keaton and Steve Carell.
Accepting his award Redmayne said he was a "lucky, lucky man".
"This belongs to all of those people around the world battling ALS," said the 33-year-old actor.
"It belongs to one exceptional family; Stephen, Jane, Jonathan and the Hawking children."
Handling his iconic statuette, he added: "I promise you I will look after him, I will polish him, I will answer his beck and call and wait on him hand and foot."
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Julianne Moore meanwhile took the best actress prize for 'Still Alice', where she plays a woman with Alzheimer's disease.
Moore said she was "thrilled" to be able to shine a light on the disease.
"People with Alzheimer's deserve to be seen so we can find a cure," she told Hollywood's elite.
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JK Simmons and Patricia Arquette earlier won the night's first acting accolades - for their supporting roles.
Simmons had been widely fancied to win for playing a fiercely intimidating jazz teacher in 'Whiplash'.
Arquette was honoured for playing the mother in coming-of-age drama 'Boyhood', filmed over 12 years with the same cast.
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Many critics had also tipped it for best film, but Birdman's late awards season momentum appeared to carry it through.
Ralph Fiennes' movie 'The Grand Budapest Hotel' also had a good night, tieing with Birdman on four gongs.
It came up trumps for costume design; make-up and hairstyling; production design and best original score. The movie started the night up with nine nods - matched by 'Birdman'.
In the technical categories there was success for 'American Sniper' (sound editing); 'Whiplash' (sound mixing); and space epic 'Interstellar' (visual effects).
Lady Gaga's tribute to The Sound Of Music for its 50th anniversary provided one of the night's musical interludes, as did best song nominee Rita Ora.
But it was Martin Luther King film 'Selma' that won best original song for Glory.
But a bum-note appeared to come from Oscars host and song-and-dance man Neil Patrick Harris.
His moment in the spotlight drew criticism from social media users, with many on Twitter saying he was "boring" and criticising his jokes.
Harris kicked off the show with a quip the night would honour the "brightest and whitest" - alluding to criticism over the lack of black nominees. The hashtag #OscarsSoWhite soon began picking up steam.
The How I Met Your Mother star then launched into a song featuring Jack Black and dancing Stormtroopers.
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Lego Movie song Everything Is Awesome also entertained the acting glitterati.
A motley crew of characters pounded out the annoyingly-catchy tune as Oprah Winfrey posed with a yellow Lego statuette.
The film was controversially snubbed in the animated film category - won on the night by Disney's Big Hero 6.
Tributes were also paid to stars who have passed away in the past year.
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