Historical actors are central to the history of knowledge as they are to all historical scholarship. Every country, every era has its biographies of eminent scientists, intellectuals, and educational reformers. Yet the theoretical currents that have left their mark on the historical and sociological study of knowledge since the 1960s have emphasized structures over actors, collectives over individuals. Knowledge Actors instead stresses the importance of historical actors and re-engages with their actions from fresh perspectives. This volume thus fosters a larger discussion among historians about the role of knowledge actors. Do we want individuals and networks to take centre stage in our historical narratives? And if so, which knowledge actors do we want to highlight and how best to conduct our research? What are the potential pitfalls of following an actor-centric path? This is the third of three volumes about the history of knowledge from the Lund Centre for the History of Knowledge (LUCK). The two other books are Forms of Knowledge and Circulation of Knowledge.