A graduate of HEC, Sciences Po Paris, and École nationale d’administration (ENA), Lucie Ruat began her career at the General Inspectorate of Finance (IGF), an interministerial body responsible for control, audit, evaluation and advisory missions on behalf of the French State.

She joined SNCF Group in 2018, initially as project lead at SNCF Mobilités, where she helped implement France’s national railway reform. On 1 January, 2020, she became Chief of Staff to Christophe Fanichet, CEO of SNCF Voyageurs, during a period marked by the Covid-19 crisis and the first steps toward opening the French market to competition.

From spring 2022 to autumn 2025, Lucie Ruat headed customer relations for the TGV Sud-Est line, overseeing teams in charge of operations and station services from the Paris-Sud-Est  the Rhône-Alpes regions.

On November 3, 2025, she was appointed Chief of Staff to Jean Castex, CEO of the SNCF group.