A genericized trademark (also known as a generic trademark, proprietary eponym) is a trademark or brand name that has become the colloquial or generic description for or synonymous with a general class of product or service, rather than the specific meaning intended by the trademark's holder. Using a genericized trademark to refer to the general form of what that trademark represents is a form of metonymy.

A trademark typically becomes "genericized" when the products or services with which it is associated have acquired substantial market dominance or mind share. A trademark thus popularized puts its legal protection at risk, as unless the owner of an affected trademark works sufficiently to prevent such broad use its intellectual property rights in the trademark may be lost.

Genericization may be either among the general population or among just a subpopulation, for example, people who work in a particular industry. Some examples of the latter type from the vocabulary of physicians include the names Luer-Lok (Luer lock) and Port-a-Cath (portacath), which have genericized mind share (among physicians) because (1) the users may not realize that the term is a brand name rather than a medical eponym or generic-etymology term, and (2) no alternate generic name for the idea readily comes to mind.

The evolution of the naming conventions of the pharmaceutical industry is linguistically interesting because it systematically avoids genericization confusion for new drug names. New drugs today have both trade names and generic names right from the beginning of their commercialization. Thus genericization examples such as aspirin, panadol, and heroin, which originated in an earlier era of drug naming practice, are less likely to occur today. Given that nowadays many new drugs are commercialized each decade, having a way to control naming clarity is important.