This report focuses on gender gaps in educational attainment and educational trajectories. It provides a review of recent research and state-of-the-art empirical evidence by examining the economic literature. It documents trends and how gender gaps vary by level of educational attainment and field of study. Existing research has documented the presence of limited gender gaps at the early stages of education. Gender gaps seem to be related to educational choices that start in high school, and then widen along the educational trajectory. This report shows that gender differences in educational choices are significant and persist over time. It also highlights the heterogeneity in gender gaps in STEM and across related sub-fields. Women are not equally under-represented in all sub-fields of STEM, yet are especially under-represented in the maths-intensive STEM fields. The available evidence suggests that the cross-country variation in gender differences in each STEM sub-field is as important as the cross-country variation in the overall STEM field. Existing studies provide evidence of a complex set of factors that explain the observed gender gaps, though the magnitude of the determinants differs across countries and over time. Among other explanatory factors, the educational context, the structure of the labour market and the environment of the workplace, as well as broader gender equality in cultural values and social norms in society, appear to play major roles. In view of the nature and magnitude of today’s gender gaps, and the fact that they vary by educational stage, different policies and interventions are needed along the educational trajectory. The current evidence on the effectiveness of policies and interventions converges toward showing the importance of teachers and role models.