Marine biological stations have offered services and biological resources to science for more than a century. ASSEMBLE Plus will provide scientists from academia, industry and policy with a quality-assured programme of Transnational Access (TA) and Virtual Access (VA) to marine biological stations offering a wide variety of marine ecosystems, unique marine biological resources, state-of-the-art experimental and analytical facilities with integrated workflows, historical observation data, and advanced training opportunities. The goal is to stimulate European excellence in fundamental and applied research in marine biology and ecology, thereby improving our knowledge- and technology-base for the blue economy, policy and education. ASSEMBLE Plus brings together 33 marine stations and institutes with modern research infrastructure and track-records of unique service provision from 14 European and associated countries under the leadership of the European Marine Biological Resource Centre (EMBRC), an ESFRI consortium developed from the previous ASSEMBLE (FP7) partnership. Joint Research Activities involving all partners aim to develop innovative new technologies and/or methodologies to be offered to users through the TA and VA programmes. A coherent series of Networking Activities (NAs) will strengthen the culture of cooperation within and beyond the consortium, providing benchmarks for refined practices of service provision, disseminating interoperable protocols, engaging with novel user communities, and sharing insights into business strategies. The sum of the actions envisaged in ASSEMBLE Plus will ultimately increase the number of users of marine biological stations and shape novel strategic development perspectives, to be based on effective integration and efficient complementarities, resulting in a key contribution to their long-term sustainability.