Violence against women and girls (VAWG) is preventable. Over the last two decades, VAWG prevention practitioners and researchers have been developing and testing interventions to stop violence from occurring, in addition to mitigating its consequences. This rigorous, in-depth review of the state of the field presents what is now known five years on after the UKAID-funded, What Works to Prevent Violence Against Women and Girls (What Works) programme, a six year investment, in advancing our understanding of What Works within the context of the wider evidence base. This review presents global evidence on what works to prevent women’s experience and men’s perpetration of physical and/or sexual intimate partner violence (IPV) and non-partner sexual violence. Child and youth peer violence is, to a limited extent, also considered, encompassing physical and verbal abuse. Overall, there is good evidence that following categories of interventions can be effective in reducing IPV and/or non-partner sexual violence globally, or physical or verbal peer violence in low- and middle-income countries, where interventions are well designed and executed: Economic transfer programmes; Combined economic and social empowerment programmes targeting women; Parenting programmes to prevent IPV and child maltreatment; Community activism to shift harmful gender attitudes, role and social norms; School-based interventions to prevent dating or sexual violence; School-based interventions for peer violence; Interventions that work with individuals and/or couples to reduce their alcohol and/or substance abuse (with or without other prevention elements); Couples’ interventions (focused on transforming gender relations within the couple, or addressing alcohol and violence in relationships); Interventions with female sex workers to reduce violence by clients, police or strangers (i.e., nonintimate partners) through empowerment/collectivisation or alcohol and substance use reduction.