In the English language, bitch (/bɪtʃ/) as a slang term is a pejorative for a person, usually a woman. When applied to a woman or girl, it means someone who is belligerent, unreasonable, malicious, controlling, aggressive, or dominant. When applied to a man or boy, bitch reverses its meaning and is a derogatory term for being subordinate, weak, or cowardly. In gay speech the word bitch can refer approvingly to a man who is unusually assertive or has the characteristics used pejoratively of a woman. The term bitch is one of the most common profanities in the English language. It has been used as a "term of contempt towards women" for "over six centuries", and is a slur that fosters sexism against women. It has been characterized as "an archaic word demeaning women since as early as the 15th century" that seeks to control women. The word is considered taboo in mainstream media, and euphemisms such as "the B-word" are used to minimize its negative impact.

The term bitch literally means a female dog. Its original use as a vulgarism carried a meaning suggesting high sexual desire in a woman, comparable to a dog in heat. The range of meanings has expanded in modern usage (such as when applied to a man). In a feminist context, it can indicate a strong or assertive woman and has therefore been reappropriated by some women.

According to the Oxford English Dictionary, the term bitch comes from the Old English word bicce or bicge, meaning "female dog", which dates to around 1000 CE. It may have derived from the earlier Old Norse word bikkja, also meaning "female dog".

"Dog" has long been used as an insult toward both women and men. In ancient Greece, dog was often used in a derogatory sense to refer to someone whose behavior was improper or transgressive. This could include shamelessness or lack of restraint, lack of hospitality, lack of loyalty, and indiscriminate or excessive violence, among other qualities. Over time, classicist C. Franco argues, a "persistent symbolic connection" developed between dogs and women in Greek literature that expressed and reinforced women's subordinate position in society and their supposedly inferior nature.

There may also be a connection between less literal senses of "bitch" and the Greek goddess Artemis. As she is the goddess of the hunt, she was often portrayed with a pack of hunting dogs and sometimes transformed into an animal herself. She was seen as free, vigorous, cold, impetuous, unsympathetic, wild, and beautiful.

The earliest use of "bitch" specifically as a derogatory term for women dates to the 15th century. Its earliest slang meaning mainly referred to sexual behavior, according to the English language historian Geoffrey Hughes:

The early applications were to a promiscuous or sensual woman, a metaphorical extension of the behavior of a bitch in heat. Herein lies the original point of the powerful insult son of a bitch, found as biche sone ca. 1330 in Arthur and Merlin ... while in a spirited exchange in the Chester Play (ca. 1400) a character demands: "Whom callest thou queine, skabde bitch?" ("Who are you calling a whore, you miserable bitch?").

Bitch remained a strong insult through the nineteenth century. The entry in Francis Grose's Dictionary of the Vulgar Tongue (1785) reads: