As part of the European Data Strategy, the European Commission is working on common European data spaces, including a Green Deal Data Space (GDDS) that covers issues such as climate change, circular economy, pollution, biodiversity, and deforestation. The successful development of the EU GDDS will depend on the availability of FAIR (findable, accessible, interoperable, and reusable) data sources, including FAIR citizen science data. While the importance of FAIR principles is increasingly acknowledged within the field of citizen science, sources of FAIR data outside the biodiversity domain are generally scarce. This is contributed by the lack of end-to-end technical solutions, readily available semantic resources to support data interoperability, and centralised data repositories suited for citizen science data. To investigate the current state of play with citizen science data FAIR compliance, we conducted a review to elicit platforms, tools and standards either used by or indicated as suitable for facilitating stages of the citizen science project lifecycle. We report on the results of our review and discuss gaps that still exist to achieve citizen science data FAIRness. We also examine three data aggregation platforms identified in our review which closely align with FAIR, namely: the Global Biodiversity Information Facility, OpenStreetMap, and Sensor.Community. [ABSTRACT FROM AUTHOR]