An index is a system used to make finding information easier.

Index may also refer to:

• Bibliographic index, a regularly updated print periodical publication that lists articles, books, and/or other information items, usually within a particular discipline.
• Index (publishing), a detailed list, usually arranged alphabetically, of the specific information in a publication
• Index cards in a rolodex or old library card catalog, early and mid 20th century technologies for maintaining such lists
• Index (mathematics), for various meanings of the word in mathematics
• Index (economics), a single number calculated from an array of prices and quantities
  • Price index, a typical price for some good or service
  • Operating Index, a tool to compare the operating performance of a company with its peer universe
• Index, Washington, a town in Snohomish County, Washington, United States
• Index, New York, a hamlet in the County and Town of Otsego, New York, United States
• Index (typography), a largely obsolete punctuation mark
• Indexing (motion), a kind of motion in many areas of mechanical engineering and machining

Publications:

• Index Librorum Prohibitorum, a list of publications which the Catholic Church censored
• Germany's List of Media Harmful to Young People, colloquially known as The Index, published by the Bundesprüfstelle für jugendgefährdende Medien
• Index Magazine, was a prominent New York City based publication for art and culture
• Truman State University Index, the weekly student newspaper
• The Index, the student newspaper of Kalamazoo College, published since 1877
• The Index (journal), a European propaganda journal created by Henry Hotze to support the Confederate States of America during the American Civil War
• index.hu, a prominent news and community portal in Hungarian
• Toaru Majutsu no Index, a Japanese light novel, manga, and anime series

In computers and information retrieval:

• Index (database), a feature in a computerized database which allows quick access to the rows in a table
• Index (information technology), either an integer which identifies an array element, or a data structure which enables fast lookup
• Index (search engine), for supporting information retrieval in search engines
• Webserver directory index, a default or index web page in a directory on a web server, such as index.html
• Subject indexing, describing the content of a document by keywords
• BitTorrent index, a list of .torrent files available for searches
• Indexed color

Other:

• The Index, an item on the Halo (megastructure) in the Halo series of video games
• The Index (Dubai), a tower under construction in Dubai
• Index (retailer), a defunct UK catalogue retailer formerly owned by the Littlewoods group and known as Littlewoods Index
• Index finger, the second digit of a human hand
• Index fund, a collective investment scheme
• Indexicality, in linguistics, the variation of meaning of an utterance according to certain features of the context in which it is uttered
• Indexed (cartoon), a web cartoon by Jessica Hagy
• In mathematics, an exponent. (Used in Australian schooling.)