Slut (archaic: slattern) is an English-language term for a person, usually a woman or girl, who is considered to have loose sexual morals or who is sexually promiscuous. It is usually used as an insult, sexual slur or offensive term of disparagement. It originally meant "a dirty, slovenly woman", and is rarely used to refer to men, generally requiring clarification by use of the terms male slut or man whore.

The word was used as early as the 1300s (in the form of an adjective, sluttish, referring to a man's untidy appearance) by Geoffrey Chaucer in The Canterbury Tales. From the late 20th century, there have been attempts to reclaim the word, exemplified by various SlutWalk parades, and some individuals embrace the title as a source of pride.