Abstract : This thesis is an academic effort to shed light on the modern aspects of the principle of good faith in the contract theory of the new French Law of Contracts after its latest amendment in 2016. It is aimed at identifying the extent of success achieved by this amendment in weeding out the legislative shortcomings that had marred the contract theory in the previous civil legislation. It also aims to inform the Arabian legal and jurisprudential community about these modern aspects and draw their attention thereto, to introspect if there is a need to review the fait accompli of this principle in their countries. The research follows a comparative, critical, analytical and descriptive legal approach. On the one hand, it analyses the modern aspects of this principle in the new French Law of Contracts, while on the other, it critically compares its current reality with the previous civil law and the Bahraini civil law in accordance with a research plan that, at its outset, presents the definition of the principle of good faith and the historical developments that accompanied its adoption into French Law. The following two chapters contain the traditional and modern concepts of good faith and its legal impact on the contract theory. The research explains how the legislators of the new French Law of Contracts generalized the principle of good faith to govern the various types of contracts and re-adapted it to make it consistent with social, economic and legal changes and make the contract theory more responsive to these changes. The research also uncovers the new legal vision that widens the protective cover of the principle of good faith for the various phases of the contract, and that the French legislator must not isolate the contract termination phase from this protection, hoping that French legislation will review its current position and provide a comprehensive protective cover to the contract.