This chapter describes the key actors in the Korean innovation system. It begins with an account of the role and performance of large national firms, in many respects the main players in Korean innovation. It then considers the role and performance of small and medium-sized enterprises (SMEs), an increasingly important sector for Korean innovation performance. It then turns to public-sector actors, starting with government research institutes (GRIs), which have played a crucial role in Korea’s ability to move into hightechnology sectors. Next, it considers Korean universities, which have played a modest though increasingly important role in research, but have been crucial for the mass education of young Korean adults. In terms of a key factor, human resources for science, technology and innovation, the chapter looks at the demand for skills and examines how overall arrangements for education and training are geared to meeting this demand. Finally, it discusses linkages between the various actors in the system with a view to assessing their strengths and overall coherence.