OBJECTIVES: To determine the prevalence in Australia of multi-type child maltreatment, defined as two or more maltreatment types (physical abuse, sexual abuse, emotional abuse, neglect, or exposure to domestic violence) and to examine its nature, family risk factors, and gender and age cohort differences. DESIGN: Retrospective cross-sectional survey using a validated questionnaire. SETTING AND PARTICIPANTS: Mobile phone random digit-dial sample of the Australian population aged 16 years and older. MAIN OUTCOME MEASURES: National estimates of multi-type child maltreatment up to age 18 years using the Juvenile Victimisation Questionnaire-R2: Adapted Version (Australian Child Maltreatment Study). RESULTS: Of 8503 participants, 62.2% (95% CI, 60.9-63.6%) experienced one or more types of child maltreatment. Prevalence of single-type maltreatment was 22.8% (95% CI, 21.7-24.0%), whereas 39.4% (95% CI, 38.1-40.7%) of participants reported multi-type maltreatment and 3.5% (95% CI, 3.0-4.0%) reported all five types. Multi-type maltreatment was more common for gender diverse participants (66.1% [95% CI, 53.7-78.7%]) and women (43.2% [95% CI, 41.3-45.1%]) than for men (34.9% [95% CI, 33.0-36.7%]). Multi-type maltreatment prevalence was highest for those aged 25-44 years. Family-related adverse childhood experiences - especially mental illness and alcohol or substance misuse - increased risk. Exposure to domestic violence was the maltreatment type most often present in multi-type maltreatment patterns. CONCLUSIONS: Multi-type child maltreatment is prevalent in Australia and more common in women and gender diverse individuals. Child protection services, health practitioners, and prevention and intervention services must assess and manage multi-type maltreatment in children and address its health consequences across the lifespan. Public health policy should consider prevention services or strategies that target multi-type child maltreatment.