The victory caps an impressive awards season for Chazelle, who is now the youngest person to ever win Best Director. Chazelle, who turned 32 last month, is a little younger than Skippy's Norman Taurog was when he won all the way back in 1931.
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During his speech, Chazelle thanked his girlfriend Olivia Hamilton, saying "This was a movie about love, and I was lucky enough to fall in love while making it."
Chazelle's ex-wife Jasmine McGlade has a producer credit on La La Land.
This is the 25th time the Oscars have split Best Picture and Best Director, which usually win together.