Iñárritu bested Wes Anderson ("The Grand Budapest Hotel"), Bennett Miller ("Foxcatcher") and Morten Tyldum ("The Imitation Game") for the honor, but Richard Linklater ("Boyhood") was his biggest competition. The two directors have gone head to head this awards season for their films in both the Best Director, Best Picture and Best Original Screenplay categories. While Linklater won for Best Director at the Golden Globes, Iñárritu took home the top prize at the Directors Guild Awards, making "Birdman" a strong lock for Academy recognition. This is Iñárritu's second Oscar.
During his acceptance speech Iñárritu said he was wearing Michael Keaton's character's tighty whities from the film, joking that they "smell like balls" (a line from the film). The director also thanked Emmanuel Lubezki, who won earlier in the night for Best Cinematography for "Birdman."
The Mexican filmmaker was also won for two other Oscars on Sunday: Best Original Screenplay and Best Picture.
Last year, Alfonso Cuarón won the Oscar for Best Director for "Gravity."
For a full list of Oscar winners, head here.