For the boardgame, see Taboo game

A taboo is a strong social prohibition (or ban), which can relate to any area of human activity or social custom declared as sacred and forbidden. Breaking of the taboo is considered abhorrent by the society. Some taboo activities or customs are prohibited under severe penalties under law. Sometimes called in slang as the forbidden fruit. Taboos can include dietary restrictions (for example, halal and kosher diets, religious vegetarianism, and the prohibition of cannibalism), restrictions on sexual activities and relationships (homosexuality, incest, bestiality, pedophilia), and use of language. When a activity or custom is classified as taboo it is forbidden and interdictions are implemented concerning the topic, such as the ground set apart as a sanctuary for criminals.

No taboo is known to be universal, but some (such as incest taboo) occur in the majority of societies. Taboos may serve many functions, and often remain in effect after the original reason behind them has expired. Some have argued that taboos therefore reveal the history of societies when other records are lacking.

Taboos often extend to cover discussing taboo topics. This can result in taboo deformation or replacement of taboo words. The word "taboo" is of Polynesian origin and its first recorded instance of use is by James Cook in 1771. The term was borrowed from the Tongan language, but appears in many other Polynesian cultures as well. In those cultures, a tapu (or tabu) often has specific religious associations.

Marvin Harris, front figure of cultural materialism, endeavoured to explain taboos as a consequence of the ecologic and economic conditions of their societies.

See also: bias, censorship, Natural law, prohibition, sacred, prejudice, social stigma