A Digital Object Identifier (DOI) is a permanent digital identifier given to an object.

Its most common application is identifying electronic documents. A DOI is not dependent on the object's location and, in this way, is similar to a Uniform Resource Name (URN) or Persistent Uniform Resource Locator (PURL) but differs from an ordinary Uniform Resource Locator (URL).

The International DOI Foundation (IDF) defines DOI name as "a digital identifier for any object of intellectual property"; it explains that the DOI is used for "persistently identifying a piece of intellectual property on a digital network and associating it with related current data in a structured extensible way.