King was based in JWT's New York office and was the global business director on the Kraft account.
In her new role, King will partner Graham Woodhall, the executive creative director at JWT Chicago, and report to the regional president for JWT Worldwide, Rob Quish. She will retain control of Kraft across 50 markets.
Quish said: "Ros is an enthusiastic and intelligent leader, who has a keen ability to deliver growth. Her experience on industries such as consumer goods, retail and alcoholic beverages made her the perfect person to lead JWT Chicago."
