The Oscar-winning actress, 31, resurfaced in London to begin shooting Thor: The Dark World -- and, appropriately enough, Portman has gone back to her dark roots!
To reprise her role as Jane Foster, the earth-dwelling romantic interest of hammer-swinging Norseman Thor (Chris Hemsworth), the star returned to the natural brunette hair that made her famous in movies like Star Wars Episode One: The Phantom Menace and Black Swan.
"Natalie makes a beautiful blonde!" her colorist, Tracey Cunningham told Us Weekly. "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."