The Mirror reported the 18-year-old actress has signed with the French fashion house a two-year contract worth $6 million.
Keira Knightley's contract with Coco Mademoiselle ends this summer.
"Emma has been excitedly telling friends that she is going to be taking over from Keira," a source told The Mirror.
Knightley has starred in the "Pirates of the Caribbean" trilogy, as well as "Pride and Prejudice" and "Atonement."
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