Counterfeit consumer goods—or counterfeit, fraudulent, and suspect items (CFSI)—are goods, often of inferior quality, made or sold under another's brand name without the brand owner's authorization. The colloquial terms knockoff or dupe (duplicate) are often used interchangeably with counterfeit, although their legal meanings are not identical.

A trademark is a type of intellectual property consisting of a recognizable sign, design, or expression that identifies a product or service from a particular source and distinguishes it from others. A trademark owner can be an individual, business organization, or any legal entity. A trademark may be located on a package, a label, a voucher, or on the product itself. Trademarks used to identify services are sometimes called service marks.