Matthew McConaughey has won the Oscar for best actor.
12 Years A Slave was named best picture.
Director Steve McQueen thanked his wife, who first showed him a copy of the original book, for "unearthing this treasure" and his parents before dedicating the win to "everyone who has endured slavery and 21 million who still do today".
Cate Blanchett was named best actress for her role in Woody Allen's Blue Jasmine, beating Bullock, Dame Judi Dench, Amy Adams and Meryl Streep in the process.
Accepting her award, she praised her fellow actresses including the "sublime" Sally Hawkins and said films with strong female characters were not "niche".
She said: "audiences want to see them and in fact they earn money".
An emotional Lupita Nyong'o picked up the first Oscar for 12 Years A Slave, winning the best supporting actress award.
The tearful star thanked director Steve McQueen for casting her in a film which she said had "been the joy of my life".
She said: "I'm certain the dead are standing about you and they are grateful and so am I".
Speaking backstage, Nyong'o said McQueen had "really honoured a people that have been unsung thorough doing this film".
The star, who admitted to feeling "a little dazed", said: "I am going to the Governors Ball and doing all things Oscar related, this is my first time here and I feel like Willy Wonka in the chocolate factory."
Earlier in the night, Dallas Buyers Club star Jared Leto was the first big winner and promised to celebrate to "the break of dawn".
Les Miserables star Anne Hathaway handed the Oscar for best supporting actor to Leto for his role as an HIV-positive transgender woman in the film.
Leto, who dedicated his win to the "36 million people who have lost the battle to Aids", beat big names including Michael Fassbender who was nominated for 12 Years A Slave.
Speaking backstage, Leto said: "I never thought this would happen, nobody talked about results or awards or potential, only how could we do the best job to bring this story to life. I never in a million years dreamed I would be here talking to you, it was a fantasy. I never dreamed they would give me a prize, I never won an award for doing anything on screen until Dallas Buyers Club.
Oscars 2014 Winners
Oscars 2014 Winners
1/8 Jared Leto : Best Supporting Actor
Jared Leto Wins for 'Dallas Buyers Club'
2/8 Lupita Nyong : Best Performance by an Actress in a Supporting Role
Lupita Nyong Wins for '12 Years a Slave'
3/8 Adruitha Lee and Robin Mathews : Best Makeup and Hairstyling
Adruitha Lee and Robin Mathews Wins for 'Dallas Buyers Club'
4/8 Peter Del Vecho, Jennifer Lee and Chris Buck : Best Animated Feature Film
Peter Del Vecho, Jennifer Lee and Chris Buck Wins for 'Frozen'
5/8 Laurent Witz and Alexandre Espigares : Best Short Film, Animated
Laurent Witz and Alexandre Espigares Wins for 'Mr. Hublot'
6/8 Nicholas Reed and Malcolm Clarke : Best Documentary, Short Subject
Nicholas Reed and Malcolm Clarke Wins for 'The Lady In Number 6'
7/8 Toni Servillo, Paolo Sorrentino, and Nicola Giuliano : Best Foreign Language Film
Toni Servillo, Paolo Sorrentino, and Nicola Giuliano Wins for 'The Great Beauty'
8/8 Christopher Benstead, Niv Adiri, Skip Lievsay, and Chris Munro : Best Achievement in Sound Mixing
Christopher Benstead, Niv Adiri, Skip Lievsay, and Chris Munro Wins for 'Gravity'
"I am going to be celebrating to the break of dawn, look me in the eyes and see I will revel tonight. If they only knew what was going to happen tonight, the stories we would have to tell."
There were two early British wins with the visual effects team behind outer-space drama Gravity picking up an Oscar before the award for best documentary short went to The Lady in Number 6: Music Saved My Life - a week after its inspiration, pianist and world's oldest Holocaust survivor, Alice Herz-Sommer, 110, died in London.
Director Malcolm Clarke, who now lives in Canada but learned his trade at the BBC and Granada TV, dedicated the win to her "extraordinary capacity for joy and her amazing capacity for forgiveness".
The event, known formally as the 86th Academy Awards, is broadcast around the world from the Dolby Theatre in Los Angeles.
Host Ellen DeGeneres opened the show with a string of gags poking fun at the event, before taking selfies of the stars and at one point ordering in pizzas.
Stars including Amy Adams got out of their chairs and danced after Kerry Washington introduced Pharrell Williams who performed his track Happy, which is nominated for best original song.
Naomi Watts and Samuel L Jackson then presented the award for costume design to Catherine Martin, the wife of director Baz Luhrmann, for her work on The Great Gatsby.
The Oscar for Best Make-up and Hairstyling was given to Dallas Buyers Club - its second win of the night.
Leto's co-star Matthew McConaughey and veteran actress Kim Novak presented the Oscar for animated short film to Mr Hublot, before the award for best animated feature went to Walt Disney film Frozen.
The award for best documentary feature went to 20 Feet From Stardom about backing singers in the music business including 1960s star Darlene Love who received a standing ovation after singing from the stage.
The technical expertise of the UK film industry was recognised when Gravity picked up awards for sound mixing and sound editing.
Bill Murray paid tribute to his Ghostbusters star Harold Ramis, who died last month, before handing over another award - this time for cinematography - to Gravity which continued to pick up awards when director Alfonso Cuaron and Mark Sanger won the Oscar for film editing.
Ramis was also remembered in a section of the ceremony dedicated to those who died in the 12 months since the last ceremony along with names including Philip Seymour Hoffman, Peter O'Toole and Richard Griffiths.
Sherlock star Benedict Cumberbatch joined Jennifer Garner on stage to present the award for production design to The Great Gatsby, before the Oscar for original score went to Steven Price for Gravity.
The musician from Nottingham praised Cuaron for inspiring him and thanked his family, joking: "Mum, Dad, Jenny sorry I made so much noise while I was growing up."
U2 lost out on the chance for an Oscar when the award for best song went to Let It Go from Frozen.Reuse content