The practice of Diamond Open Access (OA) in France provides a compelling case study of how open access principles can be systematically integrated into national research policy. Originating as a visionary idea championed by academics and activists, it has evolved into a formal, state-led strategy. This strategy has expanded further through active participation in international OA alliances and the establishment of a recognizable Diamond OA brand within France. To fully understand this complex policy landscape through qualitative text analysis of eight key French Diamond OA policy documents, this study argues that it must be examined through two complementary lenses simultaneously. First, the specific policy tools employed by the French government and agencies are analyzed. These include establishing broad legal frameworks and public digital infrastructure (environmental tools), directly funding journals and platforms (supply tools), and creating incentives for researchers to publish openly (demand tools). Second, the historical progression of these policies is traced, and divided into three distinct phases: an initial Incubation Phase of advocacy and pilot projects, a Development Phase of strategic national planning and funding, and the current Deepening Phase focused on sustainability, quality, and global leadership. Applying this two-dimensional framework to eight key policy documents, this research maps the evolution of France’ s approach over time. The analysis shows a clear and deliberate strategic shift. In early stages, emphasis was on creating the right conditions and infrastructure. As the policy matured, the focus transitioned to supporting the production of Diamond OA venues and ensuring their long-term viability. The data reveal a distinct pattern: France has consistently relied more heavily on foundational “environmental” tools and direct “supply” support, while using “demand-side” incentives more sparingly. This “strong environmental/supply, weaker demand” model contrasts with certain other European approaches. This strategic selection of policy tools has driven a significant transformation in the French research ecosystem. It has facilitated a power shift away from commercial publishing models toward a system emphasizing academic sovereignty, where scholarly communities exercise greater control over the publishing process. Ultimately, the study finds that Diamond OA policy in France is not merely about improving access to research. It also functions as a strategic instrument for enhancing France’ s influence in global science, positioning the country as a leader in the movement for a more equitable and researcher-driven scholarly communication system. The findings offer valuable insights for other nations crafting their own OA policies. For countries such as China, the French experience highlights several key priorities: building a robust legal and institutional foundation is a critical first step. Sustained, direct public investment in platforms and journals is essential to cultivate a viable Diamond OA ecosystem. Carefully combining different policy tools in a coordinated way is more effective than relying on a single approach. Furthermore, investing in the research community through training and capacity-building ensures that researchers and institutions can actively participate in and sustain the open access transition.