WikiLeaks published 75,000 classified documents about the War in Afghanistan in one of the largest leaks in U.S. military history.

WikiLeaks is a non-profit media organisation and publisher of leaked documents. It is funded by donations and media partnerships. It has published classified documents and other media provided by anonymous sources. It was founded in 2006 by Julian Assange. Kristinn Hrafnsson is its editor-in-chief. Its website states that it has released more than ten million documents and associated analyses. WikiLeaks' most recent publication of original documents was in 2019 and its most recent publication was in 2021. From November 2022, numerous documents on the organisation's website became inaccessible. In 2023, Assange said that WikiLeaks is no longer able to publish due to his imprisonment and the effect that US government surveillance and WikiLeaks' funding restrictions were having on potential whistleblowers.

The Afghan War documents leak, also called the Afghan War Diary, is a collection of internal U.S. military logs of the War in Afghanistan, which was published by WikiLeaks on 25 July 2010. The logs consist of over 91,000 Afghan War documents, covering the period between January 2004 and December 2009. Most of the documents are classified secret. As of 28 July 2010, only 75,000 of the documents have been released to the public, a move which WikiLeaks says is "part of a harm minimization process demanded by [the] source". Prior to releasing the initial 75,000 documents, WikiLeaks made the logs available to The Guardian, The New York Times and Der Spiegel in its German and English online edition, which published reports in line with an agreement made earlier the same day, 25 July 2010.

The United States government classification system is established under Executive Order 13526, the latest in a long series of executive orders on the topic of classified information beginning in 1951. Issued by President Barack Obama in 2009, Executive Order 13526 replaced earlier executive orders on the topic and modified the regulations codified to 32 C.F.R. 2001. It lays out the system of classification, declassification, and handling of national security information generated by the U.S. government and its employees and contractors, as well as information received from other governments.