International policy agendas are increasingly focusing on the 21st century skills needed by future workers in response to Industry 4.0. In this study, we conduct a bibliometric analysis of 2662 articles published by 6579 authors in the last two decades to understand the structure of the scholarly knowledge in this field. We first identify influential articles, documents, journals and trends in this literature. We use co-citation analysis to identify foundational themes in the development of 21st century skills literature, then using bibliometric coupling, we identify communities in the current research front. We then use co-word analysis to identify future directions in the field. Overall, we find that research on 21st century skills has grown exponentially in the past two decades, however, few researchers focus primarily on this topic. The existing research is primarily dominated by psychologists, education researchers and technology researchers. We also find that specific disciplines such as industrial engineering and nursing are prominent contributors in the field, and that critical thinking and computational thinking are key areas of focus.