Shylock (/ˈʃaɪlɒk/ SHY-lok) is a fictional character in William Shakespeare's play The Merchant of Venice (c. 1600). A Venetian Jewish moneylender, Shylock is the play's principal villain. His defeat and forced conversion to Christianity form the climax of the story.

Shylock's characterisation is composed of stereotypes, for instance greediness and vengefulness, although there were no legally practising Jews who lived in England during Shakespeare's time. Jews were expelled from the country in 1290 by Edward I in the Edict of Expulsion; this was not reversed until the mid-17th century (the Cromwell Era).

Shylock is not a Jewish name. However, some scholars believe it probably derives from the biblical name Shalah, which is שלח (Šélaḥ) in Hebrew. Shalah is the grandson of Shem and the father of Eber, biblical progenitor of Hebrew peoples. All the names of Jewish characters in the play derive from minor figures listed in genealogies in the Book of Genesis. It is possible that Shakespeare originally intended the name to be pronounced with a short "i" (as /ˈʃɪlɒk/ SHIL-ok), rather than a long one. In this scenario, the modern pronunciation would have changed because the standard spelling with a "y" signifies to readers a long 'i' pronunciation. Other scholars emphasise that, although the name echoes some Hebrew names, "Shylock" was a common sixteenth-century English name that would have been familiar to Shakespeare's fellow Londoners, and the name is notable for its Saxon origin, meaning "white-haired". The Shylocks of sixteenth-century London included "goldsmiths, mercers, and, most visibly of all, scriveners", according to prominent scholar Stephen Orgel, a Stanford professor who serves (with A. R. Braunmuller) as general editor of The Pelican Shakespeare series from Penguin.

Shylock is a Jewish moneylender who loans 3,000 ducats to his Christian rival Antonio, setting the security at a pound of Antonio's flesh. When a bankrupt Antonio defaults on the loan, Shylock demands the pound of flesh. This decision is fuelled by his sense of revenge, for Antonio had previously insulted, physically assaulted and spat on him in the Rialto (stock exchange of Venice) dozens of times, defiled the Jewish religion and had also inflicted massive financial losses on him. Meanwhile, Shylock's daughter, Jessica, falls in love with Antonio's friend Lorenzo and converts to Christianity, leaves Shylock's house and steals vast riches from him, which add to Shylock's rage and harden his resolve for revenge. In the end – due to the efforts of Antonio's well-wisher, Portia – Shylock is charged with attempted murder of a Christian, carrying a possible death penalty, and Antonio is freed without punishment. Shylock is then ordered to surrender half of his wealth and property to the state and the other half to Antonio. However, as an act of "mercy", Antonio modifies the verdict, asking Shylock to hand over only one-half of his wealth – to him (Antonio) for his own as well as Lorenzo's need – provided that he keeps two promises. First, Shylock has to sign an agreement bequeathing all his remaining property to Lorenzo and Jessica, which is to become effective after his demise, and second, he is to immediately convert to Christianity. Shylock is forced to agree to these terms, and he exits citing illness.

In Shakespeare's time, no Jews had been legally present in England for several hundred years (since the Edict of Expulsion in 1290). However, stereotypes of Jews as money lenders remained from the Middle Ages. Historically, money-lending had been a fairly common occupation among Jews, in part because Christians were not able to offer interest-bearing loans, then considered the sin of usury, and Jews were excluded from many fields of work. At the same time, most Christian kings forbade Jews to own land for farming or to serve in the government, and craft guilds usually refused to admit Jews as artisans. Thus money-lending was one of the few occupations still open to Jews.

Hyam Maccoby argues that the play is based on medieval morality plays, exemplum, in which the Virgin Mary (here represented by Portia) argues for the forgiveness of human souls, as against the implacable accusations of the Devil (Shylock).

Jacob Adler and others report that the tradition of playing Shylock sympathetically began in the first half of the 19th century with Edmund Kean. Previously the role had been played "by a comedian as a repulsive clown or, alternatively, as a monster of unrelieved evil". Kean's Shylock established his reputation as an actor.

Since Kean's time, many other actors who have played the role have chosen a sympathetic approach to the character. Edwin Booth was a notable exception, playing him as a simple villain, although his father Junius Brutus Booth had portrayed the character sympathetically. Henry Irving's portrayal of an aristocratic, proud Shylock (first seen at the Lyceum (London) in 1879, with Portia played by Ellen Terry) has been called "the summit of his career". Jacob Adler was the most notable of the early 20th century actors in this role, speaking in Yiddish in an otherwise English-language production.