The Assignee, when there is one, identifies the person, company, or entity other than the inventor that owns the patent. Only when an exclusive assignment of the entire right and title in the invention has been made prior to payment of the patent issue fee will an assignee be named on the patent. The patent is not re-published when later assignments are made. Usually, when an assignee appears on the face of the patent, it is the employer of the inventor(s). Assignments (including, sometimes, certain licenses) made after the patent issues should be recorded in the Patent Office by the new assignee, so that a title search will reveal the present owner and others who may have a claim to the invention.

Although the person or persons who are the inventors are always credited with the invention, and always have first ownership of it, an employer is usually the lawful owner of any invention made by any employee in the course of his or her employment. Therefore, formal written assignment by employees to their employers is usually mandatory, and, should an employee refuse, the employer will usually be able to assume title to the invention over the employee's refusal.