Browne fills the final spot on the creative agency’s executive management team, following Graeme’s departure last year alongside chairman and chief creative officer Nils Leonard and chief executive Lucy Jameson.
Having joined The Martin Agency in April 2016 as its first managing director, in London, Browne helped launch the American shop in the UK and helped it win five new clients including Dunkin Donuts and a project for Barclays.
Browne previously worked for eight years at 4Creative, Channel 4’s in-house creative agency, latterly as group business director. She helped 4Creative win its first Bafta for a digital idea and develop 4NewsWall, which reports the news using gif pictures. Channel 4 was Campaign’s Advertiser of the Year in 2015.
She was also a winner of last year’s Women of Tomorrow awards.
Before joining 4Creative in 2008, Browne spent eight years at Abbott Mead Vickers BBDO, including two years as board account director, and ran accounts for the BBC, Walkers, and Motorola.
Grey London's former chief strategy officer Leo Rayman replaced Jameson as chief executive last year, and this year Vicky Maguire was promoted to joint chief creative officer alongside Caroline Pay who joined from Bartle Bogle Hegarty.
The agency has temporarily renamed itself Valenstein & Fatt for 100 days as a tribute to its Jewish founders who launched Grey in New York 100 years ago.
As a result of Browne’s appointment, Grey London said its executive management team is now 58% female.
Rayman said: "Olivia is a leading light of the next generation of creative industry leaders. Not only has she got a super solid foundation from a traditional agency but she also brings a killer creative record from her time at 4Creative.
"Once you add in her recent entrepreneurial experience driving a small business, you have an unparalleled talent. Olivia is going to help us take Grey’s work to the next level. Can’t wait."