in bibliography, eight-digit number that provides a concise and unambiguous identification code for serial publications. Unlike the International Standard Book Number (ISBN), this number's only significance is its unique identification of a particular publication; it does not record such characteristics as subject, language, or publisher. The ISSN is used by librarians, authors, publishers, and subscription services for such various purposes as administration, copyright, ordering, and inventory control.

The ISSN was developed by a technical committee of the International Organization for Standardization. It stipulated that a “key title” should be agreed upon for assignment of a standard citation control element; serial numbers, including new assignments for a changed title, are provided through guidelines established by the International Serials Data System (ISDS). ISSN registrations are made available routinely by the U.S. Library of Congress, which includes the number on serial catalog cards and, when possible, in its publication New Serial Titles. The ISDS in Paris also makes comprehensive ISSN information available on microfiche.