She was one of the five founding partners at Work Club which was acquired by Havas in 2014. Before this she was a strategist at Mother for four years.
The move is the latest in a string of changes at the agency, including the appointment of Xavier Rees as Havas London chief executive, and Grey London’s Chris Hirst becoming Europe chief executive.
De Bonis, who reports to Rees, will help to "further enhance" Havas Creative Group’s digital offering in the newly-created role, which is an expansion of her former role as digital strategy partner.
She will continue to play a role on new business and Reckitt Benckiser Global and now will have a focus on existing Havas London client business, working with the agency's teams to convert digital opportunities.
De Bonis will also play a central role on the agency's executive management team.
Rees said: "I am incredibly excited about the team we are creating and the work we are winning. Havas London is becoming a force to be reckoned with and Lisa is a fantastic addition to the senior team.
"The role is a key strategic and commercial one, and Lisa will be an integral part of the agency's executive management team."