Ghaem-Maghami will be responsible for strengthening the network's digital capabilities and supporting agencies in the delivery of world-class interactive and e-CRM services.
Andrew Robertson, chairman of Proximity Worldwide, said: "Reze has been a key contributor to the Proximity success story since its launch in 2000. He's a true internationalist, passionate about great work and a leader that clients love."
Ghaem-Maghami joined Proximity Paris as director of business development in 2005 and has been involved in digital marketing since 1994. In 1998 he joined digital agency Framfrab, where he become chief executive of the French operation in 2000.
Owned by Omnicom and aligned with BBDO Worldwide, Proximity is represented in 50 countries and ranked the most awarded direct network in the world by The Big Won report.
The appointment follows Proximity London's hiring of OgilvyOne's chief executive Mike Dodds as chief executive, replacing Amanda Phillips, last week.