AbstractAgainst the backdrop of the increasing relevance of social media in public science communication and engagement, this study aimed to expand our understanding of the relationships and interactions between social media users and scientific outputs. In order to do so, we explored the identities, characteristics and activities of South African science tweeters (or ZA science tweeters)—i.e. Twitter users in South Africa who tweet about research articles. The growing number of ZA science tweeters, both overall and in relative terms, suggests that Twitter users are increasingly using this social media platform as a tool to share and discuss scientific outputs. ZA science tweeters are actively contributing to the sharing of information about new research articles, but, in line with global trends, the bulk of science tweets amongst South African Twitter users comes from a small number of active tweeters, and only 1% of ZA science tweeters had more than 20,000 followers. About 6.6% of ZA science tweeters are scholars (or researchers) themselves. Compared to science tweeters who are not scholars, the scholar-tweeters sent out tweets about research articles more frequently, are active on Twitter over longer periods of time, publish more original tweets and use hashtags more frequently to increase their engagement on Twitter. In their Twitter bios, these scholars typically use academic terms to describe themselves, thereby presenting themselves as experts on this social media platform. Astronomy, astrophysics, ecology and the environment emerge as the research topics that are most popular amongst ZA science tweeters.