RESUMEN
A broad understanding of the aims and objectives of the international open science movement was recently adopted with the 2021 UNESCO Recommendation on Open Science, expanding the focus of open science to include scientific knowledge, infrastructures, knowledge systems and the open engagement of societal actors. In response, recent discussions on science policy practice are shifting to the implementation of open science via national policies. While policy instruments to support some aspects of open science are well-studied, guidance on the emerging 'social' aspects of open science has lagged, prompting UNESCO to generate guidance. In this paper, several authors of the UNESCO Open Science Toolkit guidance document on 'Engaging societal actors in Open Science' synthesize the scholarly underpinnings behind its recommendations. This work draws upon a targeted search from academic, policy, and grey literature in the fields of open science and community engagement, with a special focus on citizen science, to derive guidance on how to overcome barriers to the uptake of societal engagement approaches. The results present building blocks of what an enabling environment for the open engagement of societal actors could look like, identifying key considerations and reflecting on opportunities and challenges for progressing and evaluating sound open engagement of societal actors into regional & national (open) science policies.