Here is a list of recognized interim management firms in France:
AlixPartners
Bath & Company
EY-Parthenon
McKinsey & Company
Oliver Wyman
Roland Berger
Strategy& (a division of PwC)
It is also possible to find transition management firms that are more specialized in certain areas, such as strategy consulting, digital transformation or project management. It is recommended that you do your research and request several quotes to find the firm that best suits your needs.