Mary-Kate Olsen
has gone brunette!

After sporting blonde locks for quite some time now, Mary-Kate returned to the dark side -- debuting a sleek and sophisticated new 'do at last night's Council of Fashion Designers Awards in New York City.

MK was spotted at the event with sister Ashley, who is still blonde.

The two were given the Womenswear Designer of the Year Award for their line The Row at the annual event, which is also dubbed "The Oscars of Fashion."

What do you think of the new look? We really like it!

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