The 45-year-old was visibly surprised about her victory for her performance in The Favourite, delivering an emotional and humorous speech to the star-packed audience.
Seemingly bewildered at the good news, Colman began her speech describing the experience of winning as "genuinely quite stressful" and 'hilarious'.
Period. End of Sentence. won best short documentary, and director Rayka Zehtabchi said: "I can't believe a film about menstruation just won an Oscar".
She also gave a sweet shout-out to her children, saying: "My kids, who are at home and watching".
Colman, who won for her portrayal of Britain's Queen Anne in the movie "The Favourite", appeared stunned - and, to be fair, most viewers were too - when her name was read out by fellow actress Frances McDormand. Colman is brilliant as a woman who spends most of her time in a wheelchair and is often the butt of ridicule.
But the award was snatched by Bafta victor Colman, who told her from the stage: "You have been my idol for so long, this is not how I wanted it to be".
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The image in question is from the 1970 World Cup in Mexico that Brazil went on to win. The French striker leads the club with 10 goals this season.
She became the first British victor of the award since Kate Winslet in 2009 for her portrayal of Queen Anne in the acerbic royal romp filmed in Hatfield House and the estate's gardens.
This is the first win of the night for The Favourite, the extremely queer eighteenth-century story of Queen Anne (Colman) and the women vying for her attention. And any little girl who's practicing her speech on the telly, you never know.
Bohemian Rhapsody won four awards, one more than Roma, including Best Actor for Rami Malek's performance as the late Freddie Mercury.
The film about a black jazz musician and a white driver travelling through the segregated US deep south also won the best supporting actor Oscar for Mahershala Ali, as well as best original screenplay. "I love you very much". If Beale Street Could Talk's Regina King won Best Supporting Actress and Roma's Alfonso Cuarón was named Best Director.
The actress had participated in last year's British documentary series, Who Do You Think You Are?
While Colman is taking the time to savor her win, she won't be sitting around for long.