Rebecca "Becky" Sharp, later describing herself as Rebecca, Lady Crawley, is the main protagonist of William Makepeace Thackeray's 1847–48 novel Vanity Fair. She is presented as a cynical social climber who uses her charms to fascinate and seduce upper-class men. This is in contrast with the clinging, dependent Amelia Sedley, her friend from school. Becky then uses Amelia as a stepping stone to gain social position. Sharp functions as a picara—a picaresque heroine—by being a social outsider who is able to expose the manners of the upper gentry to ridicule.

The book—and Sharp's career—begins in a traditional manner of Victorian fiction, that of a young orphan (Sharp) with no source of income who has to make her own way in the world. Thackeray twisted the Victorian tradition, however, and quickly turned her into a young woman who knew what she wanted from life—fine clothes, money and a social position—and knew how to get them. The route was to be by marriage, and the novel follows Sharp's efforts at snaring a wealthy, but simple, husband, and being outdone by fate in her attempt. Eventually, she achieves her aims, but her husband catches her with a member of the aristocracy. Finding herself in Brussels during the Waterloo campaign, as the mistress of a British general, she in no way shares in the alarm felt by other Britons; to the contrary, she soberly makes a contingency plan—should the French win, she would strive to attach herself to one of Napoleon's marshals.

It is probable that Thackeray based the Becky Sharp character on real women. A number of historical figures have been proposed, and it is generally considered that Sharp is a composite of them. Sharp has been portrayed on stage and in films and television many times, and has been the subject of much scholarly debate on issues ranging from 19th-century social history, Victorian fashions, female psychology and gendered fiction.