Systems that trained young freeborn males to become good citizens are among the most widespread institutions in the ancient Greek world. However, until relatively recently they have been neglected by scholars. In this lecture, I will sketch the spread and development of citizen training systems from their origin in 4th-century BCE Athens to their disappearance in the 4th century CE. I hope to show how a citizen training system served the community by supplying citizen-soldiers, by inculcating an ethos of physical and intellectual excellence, and by embodying the collective memory of the polis over the centuries.