The Virtual International Authority File (VIAF) is an international authority file. It is a joint project of several national libraries and operated by the Online Computer Library Center (OCLC). The project was initiated by the German National Library and the American Library of Congress.

The aim is to link the national authority files (such as the German Name Authority File) to a single virtual authority file. In this file, identical records from the different data sets are linked together. A VIAF record: receives a standard data number; contains the primary, "see", and "see also" records from the original records; and refers to the original authority records. The data are made available online and are available for research and data exchange/sharing. Data set updating uses the Open Archives Initiative protocol.

Authority control is the practice of creating and maintaining index terms for bibliographic material in a catalog in library and information science. Authority control fulfills two important functions. First, it enables catalogers to disambiguate items with similar or identical headings. For example, two authors who happen to have published under the same name can be distinguished from each other by adding middle initials, birth and/or death (or flourished, if these are unknown) dates, or a descriptive epithet to the heading of one (or both) authors. Second, authority control is used by catalogers to collocate materials that logically belong together, although they present themselves differently. For example, authority records are used to establish uniform titles, which can collocate all versions of a given work together even when they are issued under different titles.

Although theoretically any piece of information on a given book is amenable to authority control, catalogers typically focus on authors and titles. Subject headings fulfill a function similar to authority records, although they are usually considered separately.