Lindsay Pattison has been named global CEO of Maxus in a move that makes her the first female global CEO within the GroupM network of media agencies.

Maxus is the smallest of the media agencies that make up WPP's GroupM network, which also includes MEC, MediaCom and Mindshare.

Ms. Pattison, who was most recently CEO of Maxus in the U.K., succeeds Vikram Sakhuja. In a statement, GroupM said he'll remain within the group but didn't elaborate on his new role. "Under Sakhuja, Maxus was the fastest growing agency in the world," the company said in a statement. "It expanded its network footprint and added major new accounts such as NBC Universal and L'Oreal." Mr. Sakhuja had taken over as global CEO when Kelly Clark assumed the position of North American CEO of GroupM.

Under Ms. Pattison's leadership, the shop's U.K. outpost grew from 30 to 250 staffers in five years. She also held the global chief strategy officer role for the last two years, overseeing product, planning, marketing and new business. In her new role, she'll report into GroupM Global President Dominic Proctor and work in both London and New York.

"Lindsay has a proven reputation as a leader and is held with enormous regard both internally and by her clients," said Mr. Proctor in the statement. "She exemplifies the spirit and ambition of the Maxus culture, and we are confident she will take the network into the next stage of growth."

Ms. Pattison's promotion follows the recent appointment of Maxus North America CEO Steve Williams, who is also a UK native. Prior to joining in May, Mr. Williams had been president at Omnicom's PHD for two years and was previously CEO of OMD in the U.K.

Mr. Williams succeeded Louis Jones, who was named CEO of North America in 2009.