Parental monitoring is a construct of longstanding interest in multiple fields—but what is it? This paper makes two contributions to the ongoing debate. First, we review how the published literature has defined and operationalized parental monitoring. We show that the monitoring construct has often been defined in an indirect and nonspecific fashion and measured using instruments that vary widely in conceptual content. The result has been a disjointed empirical literature that cannot accurately be described as the unified study of a single construct nor is achieving a cumulative scientific character. Second, we offer a new formulation of the monitoring construct intended to remedy this situation. We define parental monitoring as the set of all behaviors performed by caregivers with the goal of acquiring information about the youth’s activities and life. We introduce a taxonomy identifying 5 distinct types of monitoring behaviors (Types 1-5), with each behavior varying along five dimensions (performer, target, frequency, context, style). We distinguish parental monitoring from 16 other parenting constructs it is often conflated with and position monitoring as one element within the broader parent-youth monitoring process: the continuous, dyadic interplay between caregivers and youth as they navigate caregivers’ attempts to monitor youth. By offering an explicit and detailed conceptualization of monitoring, we aim to foster more rigorous and impactful research in this area.