Manumission, or enfranchisement, is the act of freeing enslaved people by their enslavers. Different approaches to manumission were developed, each specific to the time and place of a particular society. Historian Verene Shepherd states that the most widely used term is gratuitous manumission, "the conferment of freedom on the enslaved by enslavers before the end of the slave system".

The motivations for manumission were complex and varied. Firstly, it may present itself as a sentimental and benevolent gesture. One typical scenario was the freeing in the master's will of a devoted servant after long years of service. A trusted bailiff might be manumitted as a gesture of gratitude. For those working as agricultural laborers or in workshops, there was little likelihood of being so noticed. In general, it was more common for older slaves to be given freedom.

Legislation under the early Roman Empire put limits on the number of slaves that could be freed in wills (lex Fufia Caninia, 2 BCE), which suggests that it had been widely used.

Freeing slaves could serve the pragmatic interests of the owner. The prospect of manumission worked as an incentive for slaves to be industrious and compliant. Roman slaves were paid a wage (peculium), which they could save up to buy themselves freedom. Manumission contracts found, in some abundance at Delphi (Greece), specify in detail the prerequisites for liberation.

Manumission was not always charitable or altruistic. In one of the stories in the Arabian Nights, in the Richard Francis Burton translation, a slave owner threatens to free his slave for lying to him. The slave says, "thou shall not manumit me, for I have no handicraft whereby to gain my living". Burton notes: "Here the slave refuses to be set free and starve. For a master to do so without ample reason is held disgraceful".