Social and cultural norms are rules or expectations of behavior and thoughts based on shared beliefs within a specific cultural or social group. While often unspoken, norms offer social standards for appropriate and inappropriate behavior that govern what is (and is not) acceptable in interactions among people. Social and cultural norms are highly influential over individual behavior in a broad variety of contexts, including violence and its prevention, because norms can create an environment that can either foster or mitigate violence and its deleterious effects. To better understand how social and cultural norms are related to violence and violence prevention, the Forum on Global Violence Prevention convened a workshop on October 29–30, 2015, to explore the social and cultural norms that underlie the acceptance of violence, with a focus on violence against women across the lifespan, violence against children, and youth violence. The workshop addressed causes, effects, characteristics, and contextual variations related to social and cultural norms related to violence; what is known about the effectiveness of efforts to alter those norms in order to prevent and mitigate such violence; and the role of multiple sectors and stakeholders in the prevention of this violence. This publication summarizes the presentations and discussions from the workshop.