This study explores the role of board gender diversity as a structural element of effective corporate governance, emphasizing its impact on financial transparency, ethical oversight, and firm performance. Supported by several theoretical frameworks such as agency theory, resource dependence, and institutional theory and supported by multicountry empirical studies, the analysis demonstrates that gender-diverse boards are more likely to constrain earnings management, promote ethical behavior, enhance oversight quality, and improve corporate performance. Moreover, this study reviews how cultural and institutional contexts influence the effectiveness of gender-inclusive governance structures. The findings support the view that gender diversity is not merely a normative goal but a strategic governance mechanism essential to long-term corporate sustainability and legitimacy. Policy implications include the importance of quota laws, inclusive nomination practices, and culturally sensitive regulatory approaches to advance meaningful representation and governance effectiveness.