Credit: Steve Granitz/

Buh-bye, scruffy tomboy K-Stew!

Kristen Stewart stole the show at Monday's red carpet premiere of Breaking Dawn: Part 1 outside the Nokia Theater in L.A.

The Twilight franchise's female star, 21, took her biggest, most dramatic departure yet from her signature everyday style (jeans, hoodies, sneakers, no makeup).

For her premiere look, Stewart (with her tresses pulled up) donned a long, sequined J. Mendel gown with a sexy, thigh-high slit that accentuated her legs and towering Jimmy Choo heels. Finishing up the look was a dazzling Neil Lane ring -- amethyst, diamonds and platinum -- worth $38,000. See more pics of Kristen on the red carpet from PopSugar.

How did Robert Pattinson's on-and-offscreen love pick out her stunning dress? "I liked it. I always go with the gut," she told Us on the red carpet. "Somebody asked me to describe it, and I was like 'Well, it's purple and it's a gown."

Tell Us: What do you think of Kristen's look?