In her acceptance speech she thanked her co-stars and her fiance, French ballet dancer and choreographer Benjamin Millepied, who she met on the movie's set and with whom she is expecting a baby.
In the film Millepied's character dismisses Portman's as someone he wouldn't want to sleep with. "It's not true. He's the best actor in the movie -- he totally wants to sleep with me," she said.
She also heaped praise on the film's director, Darren Aronofsky.
"Darren, I met you 10 years ago when we talked about this for the first time," she said. "And thank you for continuing to work on this movie and then to give me such a beautiful, beautiful gift with this role.
"Every time we finished our takes you would say, 'Now do this one for yourself.' And that gave me such beautiful inspiration as an actor to not just be a muse, that I could created on my own as well. I love you so much."
Portman had been up against Halle Berry ("Frankie and Alice"), Nicole Kidman ("Rabbit Hole"), Jennifer Lawrence ("Winter's Bone") and Michelle Williams ("Blue Valentine") for the best actress award.
The Golden Globes, launching Hollywood's annual awards season, is traditionally seen as a pointer to success at the more prestigious Academy Awards on February 27.
