"Patent pending" (sometimes abbreviated by "pat. pend." or "pat. pending") or "patent applied for" are legal designations or expressions that can be used in relation to a product or process once a patent application for the product or process has been filed, but prior to the patent being issued or the application abandoned. The marking serves to notify the public, business, or potential infringers who would copy the invention that they may be liable for damages (including back-dated royalties), seizure, and injunction once a patent is issued.

Fraudulent use of a patent pending designation is prohibited by the law of many countries and inventors should be cautious when marking products or methods that may arguably not be covered by any pending patent application. In some jurisdictions, such as the United Kingdom, a warning notice should ideally mention the number of the pending application.