This chapter looks at the enslavement of children (below 16 years of age) from the 5th to the 15th centuries, focusing on the Mediterranean and the British Isles. It uses contemporary documents, such as personal narratives, laws, contracts, letters and ecclesiastical sources, to construct case studies illustrating the major ways that children could become slaves. These include capture in war or kidnapping and sale by pirates and unscrupulous slavers; abandonment as a newborn, rescue, and rearing as a slave; pledging into servitude by parents to pay a debt; and birth to an enslaved mother. Domestic slavery was the most usual fate for children, though a few boys were made into eunuchs destined for elite households in the Byzantine Empire and the Caliphate, and girls might become concubines or sex slaves. There was little official effort to prevent child enslavement, although the Byzantine emperor Justinian attempted to abolish the use of children as debt-pledges and the enslavement of abandoned newborns, and banned castration within the bounds of his Empire. In general, the enslavement of even very young children and their transport across long distances was common and uncontroversial.