We collect a sample of 23 million parents-children matched pairs across 76 developing countries and 13,000 sub-national regions to explore the geography of intergenerational educational mobility in developing countries. First, we document large within-country variation in the degree of intergenerational mobility in educational attainment. Within-country variation accounts for more than 30% of the global variation in upward educational mobility observed across sub-national regions. Second, we uncover a strong positive relationship between intergenerational upward mobility in education and the local average educational attainment of older cohorts living in each region, as well as a strong negative relationship between upward mobility and inequality of education of these older cohorts. Third, for a sub-sample of countries with available data, we examine the sources of the within-country variation in upward mobility rates. Leveraging on children who migrate at different ages, we estimate that causal place effects explain most of the large spatial variation in mobility within countries while selection plays a minor role. The findings suggest a presence of substantial internal barriers that prohibits families to move to opportunities. We propose a simple quantitative model to assess the overall cost of these barriers.”