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."
Ron Burgundy interviews Peyton Manning on SportsCenter
Florida bear attack: Black bear mauls woman's face