Fashion Fail! Olivia Wilde Wears Dowdy Dress on Red Carpet

 Mike Marsland/WireImage.com

While promoting her two new flicks, The Change-Up and Cowboys & Aliens, Olivia Wilde (who divorced Italian prince Tao Ruspoli earlier this year), has been showing off her impressive sartorial skills in everything from red-hot structured sheaths to custom-made beaded creations.

But the star's flawless style tour came to a screeching halt when she turned heads for all the wrong reasons at the London premiere of Cowboys & Aliens on Thursday night.

PHOTOS: See Olivia in a wild 80s outfit

Wilde covered up in a black polka dot printed chiffon dress by Gucci, paired with a white bow at the neck and a slim belt. Even the side boob-revealing sheer panels and choice of bright red lipstick couldn't sex up the matronly look.

Despite the rare fashion misstep, the 27-year-old actress is having a pretty amazing week. She was just named the new global ambassador for Revlon (along with Emma Stone) and on Monday, her extra-long ponytail dressed up with clear elastics, garnered tons of praise from beauty critics who loved the unique summer 'do.

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