LCA sets the foundation for measuring resource efficiency, environmental impacts and ultimately circularity in our products and economies. The development of a national LCA database can help increase the availability of regionalized data, build local capacity in LCA, and increase the practical application of LCA in the country. This guidance document is structured into six main sections: the first summarizes the main motivations for developing a national LCA database and clarifies what constitutes an ‘LCA database’ in terms of its main characteristics. The second section presents an outline of the roadmap process conceptualized and applied in the Development of National LCA Database Roadmaps project. The third chapter describes the key elements (eight core areas) requiring consideration in the database roadmap development process, namely: (i) vision and goals; (ii) governance and management; (iii) funds and financing; (iv) human resources; (v) database hosting; (vi) data needs and availability; (vii) data quality requirements and review; and (viii) data exchange formats and interoperability. The fourth section focuses on the importance of obtaining the support from key stakeholders and securing the needed resources for developing the national LCA database. The fifth section addresses the crucial next steps to pass from roadmap development to its implementation and establishment of the national LCA database, including advice on how to manage common risks. Insights from experiences of countries from around the world with national databases development are interspaced in textboxes throughout the report. The practical examples, references, and resources provided throughout this document are intended for orientation and illustration but should not be considered exhaustive. A collection of further resources to explore, as relevant, is provided at the end of the report in section six.