Islamic religious bodies or individuals operate significant parts of education systems in various countries. In some (quite rare) cases, these schools are recognized and integrated as part of the public education system. Elsewhere, they are informal, with varying links to other parts of the system. Their roles are actively debated at national and international levels. This chapter by Lauren Herzog and Nathaniel Adams describes Islamic school systems in Bangladesh and Senegal, highlights the contemporary challenges they face, and outlines efforts to modernize and integrate the systems, led by both religious and secular actors. It was published in Religion and Education: Comparative and International Perspectives (2017) as part of the Oxford Studies in Comparative Education series.