Holding elections has become a global norm, even in autocracies; at the same time, there is mounting evidence to suggest that flawed or failed elections pose serious risks for political stability, legitimacy, and participation. Scholars and practitioners alike increasingly see domestic election monitoring groups to be a partial remedy to electoral malpractice. At least half of elections globally are monitored by such groups and large sums of international aid spent on them. However, scholarly research about the causes, dynamics, and consequences of domestic election monitoring and advocacy is scattered. This article sets out to present an overview of the academic literature on domestic monitoring. It discusses activities and actors, and presents empirical insights on the prevalence, accuracy, credibility and impartiality of monitors, as well as participation in monitoring, and its impacts on electoral integrity. It outlines gaps and open questions for a future research agenda. The review contributes to the practice, empirics and theory of election monitoring and links to broader scholarly inquiries about the embedding of human rights norms in national elections.