Multilevel governance (MLG) is one of the most successful ideas in contemporary political scholarship. Coined in the early 1990s by Gary Marks to examine developments in the European Union’s regional policy, MLG has since been adopted and further elaborated in numerous publications, which have expanded the concept well beyond its initial context, and afforded it wide currency in academic and policy-making circles. As the term turns thirty, this article maps MLG scholarship by presenting the first systematic review of this literature, based on a dataset of 590 publications. In particular, the article identifies key conceptual and empirical developments in MLG studies, assesses strengths and weaknesses of existing research, and informs future work by locating gaps and suggesting directions. By examining MLG research comprehensively, the article also provides a solid basis on which future scholarship may, possibly, reassess some of the longstanding ‘existential’ questions on multilevel governance as a research programme.