Forgery is the process of making, adapting, or imitating objects, statistics, or documents (see false document), with the intent to deceive. The similar crime of fraud is the crime of deceiving another, including through the use of objects obtained through forgery. Copies, studio replicas, and reproductions are not considered forgeries, though they may later become forgeries through knowing and willful misrepresentations. In the case of forging money or currency it is more often called counterfeiting. But consumer goods are also counterfeits when they are not manufactured or produced by designated manufacture or producer given on the label or flagged by the trademark symbol. When the object forged is a record or document it is often called a false document.

In the 16th century imitators of Albrecht Dürer's style of printmaking improved the market for their own prints by signing them "AD", making them forgeries.

In the 20th century the art market made forgeries highly profitable. There are widespread forgeries of especially valued artists, such as drawings meant to be by Picasso, Klee, and Matisse.

This usage of 'forgery' does not derive from metalwork done at a 'forge', but it has a parallel history. A sense of "to counterfeit" is already in the Anglo-French verb forger "falsify."

Forgery is one of the techniques of fraud, including identity theft. Forgery is one of the threats that have to be addressed by security engineering.

A forgery is essentially concerned with a produced or altered object. Where the prime concern of a forgery is less focused on the object itself— what it is worth or what it "proves"— than on a tacit statement of criticism that is revealed by the reactions the object provokes in others, then the larger process is a hoax. In a hoax, a rumor or a genuine object "planted" in a concocted situation, may substitute for a forged physical object.