We currently face a biodiversity crisis, driven by various anthropogenic factors such as urbanisation and agricultural land use change. Comprehensive biomonitoring methods are sorely needed to assess the current state of ecosystems and the effects of anthropogenic pressures on their composition. However, traditional approaches are costly and limited in range, thus making it difficult to expand or scale these activities. The eDNA Citizen Science project aims to upscale and expedite novel approaches for biomonitoring in an effort to help bend the biodiversity curve. To do this, we will develop and optimise a novel application that combines two transformative biomonitoring methods (citizen science and environmental DNA; eDNA) across two ecological realms (aquatic and terrestrial) and two scales (local and national). Our two-phase approach will start in and around the city of Leiden, together with local stakeholders and residents to investigate the 'nature value' of the proposed "Tweede Groene Ring". Then we will transition in the second phase to expand our eDNA citizen science framework for a national bioblitz campaign by capitalizing on already existing national networks. This project uniquely connects a multidisciplinary approach to key societal partners, anchored in policy-relevant biodiversity data.