Crom Cruach was a pagan god of pre-Christian Ireland. According to Christian writers, he was propitiated with human sacrifice and his worship was ended by Saint Patrick.

Human sacrifice is the act of killing one or more humans as part of a ritual, which is usually intended to please or appease gods, a human ruler, public or jurisdictional demands for justice by capital punishment, an authoritative/priestly figure or spirits of dead ancestors or as a retainer sacrifice, wherein a monarch's servants are killed in order for them to continue to serve their master in the next life. Closely related practices found in some tribal societies are cannibalism and headhunting. Human sacrifice is also known as ritual murder.