PIC: Blonde Natalie Portman Flaunts Hot Bod in Low-Cut, Short Dress

Actress Natalie Portman on the set of the 'Untitled Terrence Malick' movie in Austin, Texas on October 3rd, 2012.  FAMEFLYNET

That's one sexy blonde swan!

In Austin, Tex. Oct. 3, Natalie Portman continued filming an as-yet-untitled new film by director Terence Malick — and it appears her blonde bombshell makeover is complete.

The Oscar-winning actress, 31, was barely recognizable with her blonde locks pulled back in a loose ponytail and wearing a short black dress that showed off her cleavage and seriously toned legs.

"Natalie makes a beautiful blonde!" colorist Tracie Cunningham told Us Weekly of the brunette star's drastic hair switchup. "She needed to make the change for an upcoming movie role, and using Redken's Blonde Dimensions we achieved a gorgeous, multi-dimensional golden blonde."

As for her stealth sexy body, Portman is familiar with intense physical transformations. For her celebrated role as a tortured ballet dancer in Black Swan, the petite actress shed 20 pounds.

"I had never gotten that much training – to be doing five-to-eight hours a day of [it] was really a challenge," Portman told Us back in 2010.

Said her trainer and former ballerina Mary Helen Bowers: "We combined swimming a mile a day with two hours worth of Ballet Beautiful exercises, toning, and resistance work. And another 3-plus hours of ballet class and point work."

These days, however, Portman is balancing her career with marriage and motherhood. She and dancer-choreographer husband Benjamin Millepied are parents to adorable son Aleph, 16 months.

"She has this glow about her these days," a source told Us. "There's been a change in her since the little man arrived. She and Benjamin are so content."

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