Bigelows film, which also won best picture Sunday night, follows the dangerous daily existence of an Army bomb defusal team. It earned six Oscars, including one for Mark Boals original screenplay, based on his time as a journalist embedded with such a unit.
There is no other way to describe it - its the moment of a lifetime, Bigelow said, her voice quivering. She dedicated the award to the military men and women serving in Iraq, Afghanistan and around the world: May they come home safe.
Bigelow was the fourth woman nominated for the prize, following Sofia Coppola for 2003s Lost in Translation, Jane Campion for 1993s The Piano and Lina Wertmuller for 1975s Seven Beauties. She was the front runner heading into the Academy Awards.
Barbra Streisand, director of films including Yentl and The Prince of Tides, walked out on stage to present the category.
Well, the time has come, Streisand said before announcing Bigelows win.
Bigelow also bested ex-husband James Cameron, who was up for directing the sci-fi blockbuster Avatar - and shed been sitting directly in front of him all night during the Oscar ceremony. Much has been made about the former spouses competing against each other, but their split was amicable and the two since have supported each other professionally. As Bigelows victory was announced, Cameron could be seen clapping and saying, Yes, yes.
Backstage, reporters repeatedly tried to coax her to dish on her ex, but she was abidingly diplomatic.
I think hes an extraordinary filmmaker, she said, when asked what it was like to beat him.
Bigelow had already been a pioneer for decades, having built a career making action pictures like Point Break and K-19: The Widowmaker, usually male-dominated territory. But at the Directors Guild of America Awards, where she won the top honor, Bigelow said: I suppose I like to think of myself as a filmmaker - not a female filmmaker.
And now, she can think of herself as an Oscar winner.