A graduate of the Ecole Polytechnique, Ensae ParisTech and Pompeu Fabra University in Barcelona, Stéphane Lhermitte began his career in 2002 as a research officer at France's national statistics office, INSEE, before becoming a research officer at ARCEP in 2005. He later became Head of the Fixed market regulation unit, then head of the Mobile market unit. 

In 2008, Stéphane joined the National Treasury where he was in charge of the Office of Financial research, before being appointed Head of the Economic Department of the French Embassy to Portugal.

On 1 September 2014, Stéphane Lhermitte will take up the position of ARCEP's Director of Economic affairs and forward planning.