National geoheritage inventories constitute fundamental tools for geoconservation, providing the scientific basis for the identification, assessment, management, and protection of geological heritage. In Portugal, two independent national inventories were developed during the last two decades by the University of Minho (UMinho) and by the Portuguese Geological Survey (LNEG), resulting in partially overlapping databases with different structures and territorial coverage. This paper presents the development of a unified National Inventory of Geological Heritage (NIGH), created through the merging, harmonisation, and expansion of these two previous initiatives. The methodology involved a comparative analysis of both inventories, the development of a relational database, the standardisation of data fields, GIS-based georeferencing, and the implementation of an online dissemination platform within the LNEG GeoPortal. The resulting inventory currently comprises approximately 400 geosites distributed across mainland Portugal and the two Autonomous Regions of the Azores and Madeira, organised into 26 geological frameworks representative of the country’s geodiversity and its geological evolution. The database stores detailed information on geological characteristics, scientific relevance, conservation status, vulnerability, and management requirements, while ensuring ongoing updating through the participation of experts coordinating the different geological frameworks. The NIGH represents the most comprehensive national geoheritage database developed in Portugal to date and provides an essential tool for geoconservation, spatial planning, environmental management, research, education, and geotourism. Remaining challenges include geosite delimitation, legal protection, institutional integration within conservation policies, and the long-term sustainability of the inventory. The NIGH establishes a robust foundation for the future development of proactive geoconservation strategies in Portugal.