You do not need to speak French before coming to ESSEC. The academic language of the programme is English so you will have no problem at all with the courses.
For everyday life on the Cergy campus (and in Paris in general), it will be much easier however, if you master basic proficiency in French and we encourage you to embrace learning the language as well as of course other foreign languages. If for example, you are a beginner, in your 1st year, you will have 6 hours of French classes per week on different themes i.e. business, day to day, etc. An additional 3 hours will be spent learning another language.