The integrated European Long-Term Ecosystem, critical zone and socio-ecological Research Infrastructure (eLTER RI) is a distributed Research Infrastructure aiming at integrating traditional natural sciences and holistic ecosystem research approaches, including studies of the human component, to better understand ecosystems. Through research and observation, eLTER RI seeks to improve our knowledge of the structure and functions of ecosystems and their long-term response to environmental, societal and economic drivers. eLTER RI will consist of Central Services (Head Office, Service Portal and Topical Services) and about 250 eLTER Sites and Platforms providing services like access to data and sites for various user groups and research communities. eLTER will provide indispensable integrated data sets – abiotic, biotic, societal, covering all system structures and functions – for system model development and validation, hence supporting predictions and decision-making in an interdisciplinary framework. eLTER RI contributes to the knowledge base informing policy and to the development of management options in response to the Grand Challenges under Global Change. The mission of eLTER is to facilitate high impact research and catalyse new insights about the compounded impacts of drivers like climate change, biodiversity loss, soil degradation, pollution, and unsustainable resource use on a range of European ecosystems and socio-ecological systems, representing the “critical zone” in which we live. With our distributed infrastructure and scientific expertise, we aspire to provide users with the scientific capacity to improve our understanding of terrestrial, freshwater, and transitional water ecosystems, and a solid foundation to inform evidence-based policy making and management solutions for addressing current and emerging environmental challenges. eLTER is a distributed pan-European in-situ research infrastructure that will serve multiple scientific communities with high-level central services and well-instrumented eLTER Sites and socio-ecological eLTSER Platforms Continent-wide, novel data services and products will result from combining harmonised standard observations at the sites with decades of legacy data and information from a wide range of other sources. These services will be accessible to a broad diversity of stakeholders from local to continental scales. As a fundamental component of eLTER's identity, we will synergistically collaborate with diverse ecosystem/environmental research infrastructures and networks across Europe and the world. Strategic goals: The first goal is to facilitate innovative research for addressing grand societal challenges. We strive to enhance the scientific capacity, efficiency, and visibility of the European Research Area, supporting sustainable management and policy-making in environmental issues. eLTER integrates researchers across ecosystem ecology, biodiversity, critical zone, and socio-ecological systems to tackle societal challenges systemically. Through our distributed in-situ facilities across Europe, we develop and deploy innovative research methods to address these challenges. The second goal is to design and operate a distributed and highly functional network of eLTER in-situ facilities across Europe. We integrate eLTER Sites and Platforms into a pan-European research infrastructure, supported by centralised services for site- and continent-scale research. The third goal is to create a unique and widely accessible service portfolio that serves as the central gateway for accessing harmonised data from eLTER in situ facilities and other centralised services. We actively seek collaboration opportunities with both external and internal users to co-develop tools and services through technical and strategic partnerships. The fourth goal is to promote collaboration, integration, and a conducive working culture. We prioritise high ethical and environmental standards and foster collaborations with RIs globally, and cultivate a collaborative internal culture, promoting transdisciplinary research and investing in the diversity of our research community.