This is the actresses' second Oscar win.
Blanchett previously won a Best Supporting Actress Oscar in 2005 for "The Aviator."
Blanchett beat out Sandra Bullock ("Gravity"), Amy Adams ("American Hustle"), Judi Dench ("Philomena"), and Meryl Streep ("August: Osage County").
The 42-year-old actress won the Best Actress award at both the Golden Globes and BAFTA Awards.