Adverse childhood experiences (ACEs), including child maltreatment and other adversities in the home context and beyond (e.g., witnessing domestic violence; parental mental illness; parental separation; living in a disadvantaged neighborhood) are prevalent in the population and often covary together. Research based on the construct of ACEs has transformed the field of adult mental health, yet child and adolescent mental health has often been overlooked in this work. This special issue of Research on Child and Adolescent Psychopathology focuses on the developmental science of ACEs and child psychopathology. The research presented here draws on the extensive evidence base that now exists regarding the co-occurrence of common childhood adversities, while informing the integration of theory and research on ACEs with that of developmental psychopathology at large. This Introduction provides an overview of ACEs and child mental health from a developmental psychopathology perspective, with an emphasis on key concepts and recent progress spanning the prenatal period through to adolescence and intergenerational pathways. Models of ACEs that emphasize the multi-dimensional nature of adversity and the importance of developmental timing to risk and protective pathways, have played a driving role in this progress. Methodological innovations in this work are highlighted, along with implications for prevention and intervention.