To become sustainable over time, European research infrastructures must increase their visibility, both individually and collectively. This requires the harmonization of the strategies, tools, guidelines and resources that European research infrastructures use in their communication. This toolkit is a collective effort of 31 communication experts representing 17 research infrastructures to provide an easy and useful set of communication tools, guidelines and resources adapted to the needs, constraints and capacities of European research infrastructures. The “Communication Toolkit for European Research Infrastructures” includes: A style guide, comprised of a glossary, a jargon buster and key messages; A website, including guidelines for navigation and the “about us” page, along with contents for a “about EU research infrastructures” webpage A social media strategy and common hashtags Resources, including general PowerPoint slides and strategies to address different targets (private sector, decision-makers and research infrastructures outside of Europe).