Agnes Audier's role will be to increase the efficiency and productivity of the group, especially by cutting costs. She will also join the company's executive committee.
In September, Havas announced a major restructure and hundreds of job losses, particularly in the UK, in an attempt to get back on course after posting a first-half net loss of £40m.
The company said at the time it had identified around 50 out of 350 companies that were bringing down the rest of the group and said that these would either be sold or closed.
Audier has spent the past six years at Vivendi Universal, where she was director of strategy and development, and was involved in the post-acquisition integration of US Filter and Seagram/Universal.
She also headed up the Vivendi Universal internet and technology division, including the restructuring of the company after the dotcom bubble burst.
Before joining Vivendi, Audier was an adviser to the French minister of health and the minister of small businesses.
Havas chairman and chief executive Alain de Pouzilhac said: "I am delighted that Agnes has agreed to join Havas. She is a consummate professional who has already proved her worth in various sectors, including the media. She will have a key role to play in improving profitability, which is one of our top priorities."
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