Plastic pollution has become a global environmental and societal concern in recent years. Numerous protocols have been developed to monitor plastic debris, but these are rarely comparable. This has hindered gathering of knowledge regarding pollution sources, development of monitoring programmes and risk assessments and implementation of mitigation measures. To develop long-term solutions to reduce plastic pollution, it is essential to establish harmonised methodologies. EUROqCHARM will address this by critically reviewing state-of-the-art analytical methods and, taking harmonisation one step further, validating them through an interlaboratory comparison (ILC) study. This will bring together prominent laboratories in environmental plastics analysis and will produce certified reference materials to be marketed for at least three of the four target matrices (water, soil/sediment, biota, air), during and after project completion. EUROqCHARM recognises that harmonisation for large scale monitoring requires flexibility, comparability and reliability. We will identify Reproducible Analytical Pipelines (RAP), resulting in a catalogue of RAP procedures for nano-, micro- and macro-plastics for the four target matrices. Each RAP will be validated in terms of Technology Readiness Level to decide if further validation is needed (by ILC). Blueprints for standards, recommendations for policy and legislation and support for the establishment of acceptable reference levels and environmental targets will be given. This will include a roadmap for harmonised data collection and management, where policy analysis and coherence will be integral parts. To maximise impact, EUROqCHARM will also establish and consolidate an operational network for plastic monitoring, stimulating Transnational Joint Actions built on existing and future European and international initiatives. The multi-stakeholder composition of EUROqCHARM puts the group in a unique position to achieve these ambitious goals.