What does the American public know about child marriage?

Global efforts to eradicate 'child marriage' (<18 years) increasingly target governments, the private sector and the general public as agents of change. However, understanding of child marriage may be subject to popular misconceptions, particularly because of ambiguity in the age threshold implied by the term 'child', and because awareness campaigns routinely emphasize extreme scenarios of very young girls forcibly married to much older men. Here, we ascertain public knowledge of child marriage via an online survey. Half of those surveyed mistakenly believed that the cut-off for child marriage is younger than the threshold of 18 years, and nearly three-quarters incorrectly believed that most child marriages occur at 15 years or below (it primarily occurs in later adolescence). Most participants also incorrectly believed that child marriage is illegal throughout the USA (it's illegal in only 4/50 states), substantially overestimated its global prevalence, and mistakenly believed that it primarily takes place among Muslim-majority world regions. Our results highlight important popular misconceptions of child marriage that may ultimately undermine global health goals and perpetuate harmful stereotypes. Organizations seeking to empower women by reducing child marriage should be cautious of these misunderstandings, and wary of the potential for their own activities to seed misinformation.