A charlatan is a person practicing quackery or some similar confidence trick in order to obtain money or advantage by false pretenses. If the ascription is false, then "charlatan" is pejorative; if it is true, then the description "charlatan" is no libel.

The word comes from French charlatan, a version of "Charley," a seller of medicines who might advertise his presence with music and an outdoor stage show. The greatest of the Parisian charlatans was Tabarin who set up a stage in the Place Dauphin, Paris from 1618, and whose commedia dell'arte-inspired skits and farces inspired Molière. Ultimately, etymologists trace "charlatan" from either the Italian ciarlare, to prattle; or from Cerretano, a resident of Cerreto , a town that was apparently notorious for producing quacks.

In usage, a subtle difference is drawn between the charlatan and other kinds of confidence people. The charlatan is usually a salesperson. He does not try to create a personal relationship with his marks, or set up an elaborate hoax using roleplaying. Rather, the person called a charlatan is being accused of resorting to quackery, pseudoscience, or some knowingly employed bogus means of impressing people in order to swindle his victims by selling them worthless nostrums and similar goods or services that will not deliver on the promises made for them. The word calls forth the image of an old time medicine show operator, who has long left town by the time the people who bought his snake oil tonic realize that it does not perform as advertised.

Synonyms for "charlatan" include "mountebank" and "quack".