He replaces former chief executive Joanna Shields who drove Bebo's sale to AOL in March last year. Shields became head of AOL's People Networks division last May, before returning to London to pursue start-up ventures.
AOL's People Networks division has since been axed and replaced with a new unit called AOL Ventures.
Panier was previously vice president and chief operating officer of Bebo. In his new role, Panier will report directly to Jon Brod, executive vice president, AOL Ventures.
Brod said: "Stephane is a proven strategist and operator with executive experience from some of the world's leading brands and businesses.
"He is the ideal leader to build on Bebo's existing successes, to chart a course for its future, and to execute against that vision."
Panier has more than a decade's experience spanning finance, operations and strategic consultancy.
Before joining in January 2009, Panier worked for for six years in both senior finance and operations positions. He also provided support to Google's Adsense business.
Panier said: "The past nine months have seen us create and deliver a more relevant and open social experience for our users across both new and existing markets, and I look forward to building on this foundation.
"We have a strong and talented team and as we advance we will continue to concentrate our efforts on delighting users and carving out our place as a market leader."
The appointment comes as Time Warner prepares to float AOL. Earlier this week, it paid $283m for Googe's three-year-old stake in AOL, which values the online firm at $5.7bn.