Sponsored editorial content is material with similar qualities and format to content that is typically published on a platform or by a content provider, but which is paid for by a third party. The growth of sponsored content in digital journalism over the last two decades has attracted wide-ranging research into developing practices, arrangements and their industrial, cultural and societal consequences. This introduction to a special issue on sponsored editorial content discusses the phenomena and how it has been understood and addressed by academic researchers, industry practitioners, regulatory agencies and civil society stakeholders. The article discusses definitions and definitional debates, provides a mapping of research approaches and findings, and identifies paths for future research, including those developed by authors for this special issue.