After Francis' arrival Nigel Sharrocks, currently CEO of Western Europe for Aegis Media, will take global responsibility for its three media networks Carat, Vizeum and Posterscope and oversee the international client teams for those brands.
Aegis Media's performance marketing network iProspect and creative network Isobar remain under the global oversight of Mark Cranmer.
Sharrocks will also become chairman of Aegis Media UK.
Francis will sit on Aegis Media's global executive board and report to Aegis group chief executive Jerry Buhlmann.
Francis' last media agency role before joining Saatchi & Saatchi in 2007 was EMEA managing director at Omnicom network OMD. His previous roles include strategic planning director at Mindshare UK.
Buhlmann said: "Simon has a wealth of experience both in the sector and the region with an impressive track record which speaks for itself."