Abstract Background Child maltreatment is a complex public health issue that has consequences across the life-course. Studies to measure child maltreatment and identify interventions and services are constrained by a lack of uniform definitions across sectors and countries. We conducted a Delphi study to reach consensus on types and characteristics of child maltreatment for use in surveillance and research in Europe. Methods Statements were developed following a scoping review and identification of key concepts by an international expert team (n = 19). A multidisciplinary expert panel (n = 70) from 34 countries participated in three rounds of online data collection. We defined consensus as ≥ 70% agreement or disagreement with each statement after the final round. Results Consensus was reached on 26/31 statements, with a participant retention rate of 94%. The definition states that child maltreatment is a subtype of violence against children. The perpetrator can be an adult or minor, but must be in a position of power over the child. To define an act or omission as child maltreatment, it must cause harm or have the potential to cause harm, regardless of intention, severity, chronicity, or the traditional/cultural beliefs of the perpetrator. In addition, the broad umbrella term encompassing emotional, behavioural or cognitive maltreatment should be “psychological”, and psychological maltreatment should be split into sub-types of psychological abuse and psychological neglect. “Neglect” is a broad type of child maltreatment within which there are subtypes that can all be characterised as “failure to provide” or “failure to supervise”. Conclusions This is the first study to demonstrate consensus on the types and key characteristics of child maltreatment across multiple sectors and countries, providing a unified definition of child maltreatment to improve consistency of measurement and surveillance in Europe. This abstract is submitted on behalf of Working Group 1 COST Action 19106. Key messages • A standardised definition is essential for monitoring child maltreatment. • We propose a consensus-based definition that can be used to improve child maltreatment measurement in research and surveillance.