The World Factbook (ISSN 1553-8133; also known as the CIA World Factbook) is a reference resource produced by the Central Intelligence Agency of the United States with almanac-style information about the countries of the world. The official paper copy version is available from the National Technical Information Service and the Government Printing Office. Other companies—such as Skyhorse Publishing—also print a paper edition. The Factbook is available in the form of a website, which is partially updated every week. It is also available for download for use off-line. It provides a two- to three-page summary of the demographics, geography, communications, government, economy, and military of 267 entities including U.S.-recognized countries, dependencies, and other areas in the world.

The World Factbook is prepared by the CIA for the use of U.S. government officials, and its style, format, coverage, and content are primarily designed to meet their requirements. However, it is frequently used as a resource for academic research papers. As a work of the U.S. government, it is in the public domain in the United States.