Castration (also known as gonadectomy) is any action, surgical, chemical, or otherwise, by which an individual loses use of the testicles. Surgical castration is bilateral orchiectomy (excision of both testes), and chemical castration uses pharmaceutical drugs to deactivate the testes. Castration causes sterilization (preventing them from reproducing); it also greatly reduces the production of certain hormones, such as testosterone. Surgical castration in animals is often called neutering. The term "castration" is sometimes also used to refer to the removal of the ovaries in the female, otherwise known as an oophorectomy or, in animals, spaying. Estrogen levels drop precipitously following oophorectomy, and long-term effects of the reduction of sex hormones are significant throughout the body.
Castration of non-human animals is intended to favor a desired development of the animal or of its habits, as an anaphrodisiac or to prevent overpopulation.
Castration was frequently used for religious or social reasons in certain cultures in Europe, South Asia, Africa, and East Asia. After battles in some cases, winners castrated their captives or the corpses of the defeated to symbolize their victory and seize their "power". Castrated men — eunuchs – were often admitted to special social classes and were used particularly to staff bureaucracies and palace households: in particular, the harem. Castration also figured in a number of religious castration cults. Other religions, such as Judaism, were strongly opposed to the practice. The Leviticus Holiness code, for example, specifically excludes eunuchs or any males with defective genitals from the priesthood, just as castrated animals are excluded from sacrifice.