A cuckold is the husband of an adulterous wife. In evolutionary biology, the term is also applied to males who are unwittingly investing parental effort in offspring that are not genetically their own.^[1]

The word cuckold derives from the cuckoo bird, alluding to its habit of laying its eggs in other birds' nests.^[2][3] The association is common in medieval folklore, literature, and iconography.

English usage first appears about 1250 in the medieval debate poem The Owl and the Nightingale. It was characterized as an overtly blunt term in John Lydgate's "Fall of Princes", c. 1440.^[4] Shakespeare's writing often referred to cuckolds, with several of his characters suspecting they had become one.^[3]

The word often implies that the husband is deceived; that he is unaware of his wife's unfaithfulness and may not know until the arrival or growth of a child plainly not his (as with cuckoo birds).^[3]

The female equivalent cuckquean first appears in English literature in 1562,^[5][6] adding a female suffix to the cuck.

A related word, first appearing in 1520, is wittol, which substitutes wit (in the sense of knowing) for the first part of the word, referring to a man aware of and reconciled to his wife's infidelity.^[7]

In Western traditions, cuckolds have sometimes been described as "wearing the horns of a cuckold" or just "wearing the horns".

This is an allusion to the mating habits of stags, who forfeit their mates when they are defeated by another male.^[8] In Italy (especially in Southern Italy, where it is a major personal offence), the insult is often accompanied by the sign of the horns. In French, the term is "porter des cornes", which is used by Molière to describe someone whose consort has been unfaithful. In German, the term is "jemandem Hörner aufsetzen", or "Hörner tragen", the husband is "der gehörnte Ehemann". Rabelais wrote the Tiers Livers of Gargantua and Pantagruel in 1546, by which time the symbol of the horns was "so well-known and over-used that the author could barely avoid making reference to it".^[9] Molière]]'s cks cuckolds and becomes one at the end. In Geoffrey Chaucer's Canterbury Tales (c. 1372–77), "The Miller's Tale" is a story that humorously examines the life of a cuckold. In Chinese usage, an altogether different allusion is used, when the cuckold (or wittol) is said to be "戴綠帽子" (wearing the green hat), which derives from the sumptuary laws used in China from the 13th to the 18th centuries that required the males in households with prostitutes to wrap their heads in a green scarf (or later a hat).^[10]

An abbreviation of cuckold, the term cuck has been used by the alt-right to attack the masculinity of an opponent. It was originally aimed at other conservatives, whom the alt-right saw as ineffective.^[11]

Unlike the traditional definition of the term, in fetish usage a cuckold or wife watching is complicit in their partner's sexual "infidelity"; the wife who enjoys cuckolding her husband is called a hotwife or a cuckoldress or if the man is more submissive.^[12][13][14] If a couple can keep the fantasy in the bedroom, or come to an agreement where being cuckolded in reality does not damage the relationship, they may try it out in reality. However, the primary proponent of the fantasy is almost always the one being humiliated, or the "cuckold": the cuckold convinces his lover to participate in the fantasy for them, though other "cuckolds" may prefer their lover to initiate the situation instead. The fetish fantasy does not work at all if the cuckold is being humiliated against their will.^[15]

Psychology regards cuckold fetishism as a variant of masochism, the cuckold deriving pleasure from being humiliated.^[16][17] In Freudian analysis, cuckold fetishism is the eroticization of the fears of infidelity and of failure in the man's competition for procreation and the affection of females. In his book Masochism and the Self, psychologist Roy Baumeister advanced a Self Theory analysis that cuckolding (or specifically, all masochism) was a form of escaping from self-awareness, at times when self-awareness becomes burdensome, such as with perceived inadequacy. According to this theory, the physical or mental pain from masochism brings attention away from the self, which would be desirable in times of "guilt, anxiety, or insecurity", or at other times when self-awareness is unpleasant.^[18]