Lepere will co-ordinate the network's new-business teams from around the world. He will report to Heekin, the recently appointed president and chief operating officer.
He will be required to oversee all areas of the network's marketing strategy.
This responsibility includes furthering the Euro RSCG brand and cementing relationships with international clients. He will begin on 17 November and be based in London.
Lepere was previously an executive vice-president at McCann-Erickson Worldwide, working under Heekin, who was then the chairman and chief executive of the network. During his time at McCann, Lepere led the agency's $500 million Microsoft account. He also held the position of deputy chairman.
The appointment was motivated by Euro's attempts to reposition itself as a full-service provider. In various markets around the world, the network has melded its main ad agencies with direct marketing shops, PR outfits and publishing divisions under the banner of The Power of One.
Earlier this year, Euro RSCG Wnek Gosper merged with the Havas agency Partners BDDH to create a top ten UK agency at the heart of the UK Euro RSCG Group.
Heekin said: "Marc is a proven international leader with an established track record in meeting key challenges and in capitalising on business opportunities. With his joining us, we are well-positioned to drive winning creative ideas across multiple communications channels in order to extend our clients' business success."
Lepere added: "Clients around the world are demanding real, true integration, and not just in name. Euro RSCG has exactly that. I look forward to evolving and growing the network's offering in this area."
In addition, Havas has appointed Agnes Audier to the role of chief performance officer. Audier will report directly to the Havas chairman and chief executive, Alain de Pouzilhac, and will be a member of the holding company's executive committee.