While economists have extensively studied gender norms affecting women, masculinity norms – the informal rules that guide and constrain the behaviours of boys and men – remain underexplored. This column reviews how such norms can shape economic outcomes in labour markets, health, education, households, and politics. Drawing on new survey data from 87,000 individuals across 70 countries, the authors show that adherence to masculinity norms strongly predicts men's labour supply, risk-taking, health behaviours, and support for authoritarian leadership.