He beat Adam Driver (BlacKkKlansman), Sam Elliott (A Star Is Born), Richard E Grant (Can You Ever Forgive Me?) and Sam Rockwell (Vice).
"I want to dedicate this to my Grandmother, who has been in my ear my entire life," he said. "Always, always pushing me to do something better."
Fellow winners on the night included Regina King for Best Supporting Actress, who took home the statuette for her role in If Beale Street Could Talk.
The 2019 Oscars saw Rami Malek take home Best Actor for his portrayal of Freddie Mercury in Queen biopic Bohemian Rhapsody. Other winners included Olivia Colman for The Favourite and Alfonso Cuarón took home Best Director for his Netflix drama Roma. Green Book won Best Picture, proving a controversial choice over Roma.
You can find a full list of winners here.
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