Gender inequality remains pervasive worldwide. While in some countries boys and men may be at a disadvantage in some areas, in most countries girls and women continue to bear the brunt of gender inequality. For this reason, this study focuses on the impacts of gender inequality on girls and women. To make the case for more and better investments to reduce gender inequality, the study provides estimates of the impacts and economic costs of gender inequality in five main domains of interest: (1) earnings and standards of living; (2) educational attainment, child marriage and early childbearing; (3) fertility and population growth; (4) health, nutrition, well-being, and violence; and (5) agency, decision-making, and social capital.