The actress, who previously won supporting actress for "The Aviator" in 2004, thanked Allen in her speech for writing the script and casting her after a six-year hiatus from film doing theater work in Sydney.
Daniel Day-Lewis, who won his third lead actor award (the only person to do so) last year for "Lincoln."
Blanchett had been hotly anticipated to take home the trophy ever since the film's release last summer. She won over fellow lead actress nominees Amy Adams, Meryl Streep, Sandra Bullock and Judi Dench.
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