This study investigates the impact of board characteristics on the Environmental, Social, and Governance (ESG) performance of French listed companies. Grounded in a multi-theoretical framework integrating agency, resource dependence, legitimacy, and critical mass theories, we examine how board size, independence, gender diversity, and the presence of a sustainability committee influence ESG ratings. Using a panel dataset of 158 non-financial companies from the SBF 250 index over the period 2016-2024, we employ fixed-effects regression models with lagged governance variables to address endogeneity concerns. The results reveal that robust and diverse governance structures are fundamental drivers of superior ESG performance. Specifically, the presence of a dedicated sustainability committee and a critical mass of at least three female directors are identified as the most potent and consistent predictors of higher ESG scores. The analysis also confirms the value of independent oversight and collective knowledge, with both board independence and larger size demonstrating a significant positive influence on ESG ratings. The findings highlight that in France's distinctive stakeholder-oriented and highly regulated environment, deliberate board composition is essential for translating governance into tangible sustainability outcomes. This study provides actionable insights for corporate boards and validates the effectiveness of regulatory interventions aimed at enhancing corporate governance.