Forests are key elements of the European bioeconomy. To enhance provision of their ecosystem services (ES), harnessing Forest Genetic Resources (FGR) is essential. OptFORESTS will support the conservation and sustainable use of FGR by: i) conducting research on the selection of diverse forest reproductive material (FRM), including mixtures, adapted to future climates, ii) fostering sustainable use and resilience of natural forests, iii) helping expand and diversify nursery production, iv) developing nature-based solutions (NBS), tools (e.g., expanded Information Systems) and cultural trajectories to promote forest biodiversity and ES, and v) demonstrating biodiversity restoration solutions. To do this, OptFORESTS will carry out genetics, modelling, stakeholder surveys, expert panels and socioeconomic analyses. OptFORESTS will evaluate adaptive and biomass traits in existing common gardens and newly-established next-generation ones, conserve and utilise unique tree lineages for ecosystem restoration and management, model future adaptation of trees at different life stages and conduct low-input breeding. This will be complemented by studying the effects of silviculture and landscape heterogeneity on genetic diversity and developing new silvicultural options for genetically mixed forests, which will be implemented via training software (marteloscopes) and long-term demonstration plots. To enable optimal supply of diversified FRM, OptFORESTS will assess the European nursery sector, forecast future FRM needs, develop plant production technology and promote cooperation between nurseries. To ensure the uptake of NBS, they will be co-designed with local and EU-level stakeholders and a cost-benefit and gap analysis of key socio-economic, governance and policy issues will be developed. Finally, the OptFORESTS tailored communication strategy will be instrumental in achieving long-term impacts supporting international and EU policy under the European Green Deal.