The Five Eyes (FVEY) is a post-World War II intelligence alliance and concept, not a formal act or provision, comprising five Anglophone nations: the United States, the United Kingdom, Canada, Australia, and New Zealand. Its origins trace back to secret meetings between British and American code-breakers at Bletchley Park in 1941. The alliance was formally established by the UKUSA Agreement on March 5, 1946, initially between the US and UK, to facilitate intelligence sharing and combat the Soviet Union during the Cold War. Canada, Australia, and New Zealand were formally included by 1955 or 1956.
The alliance functions as an informal network linking the intelligence agencies of the member states, such as the US National Security Agency (NSA) and the UK's Government Communications Headquarters (GCHQ). Its core mechanism is the comprehensive sharing of intelligence, including signals intelligence (SIGINT), military intelligence (MILINT), and human intelligence (HUMINT). The alliance developed the global ECHELON surveillance system in the 1960s to monitor communications. The term "Five Eyes" originated as a shorthand for the "AUS/CAN/NZ/UK/US Eyes Only" releasability caveat.
The FVEY concept connects to broader intelligence-sharing groups like Nine Eyes and Fourteen Eyes, which include European partners. The alliance has adapted its focus from the Cold War to global surveillance, counter-terrorism, and cyber threats. Recently, the alliance has focused on modern challenges, such as publishing joint guidance on agentic Artificial Intelligence (AI) security in 2026 and working to align military fuel standards for interoperability. There is also an ongoing discussion regarding the potential for Japan to achieve deeper integration with the alliance. Revelations by Edward Snowden in 2013 brought the alliance into public scrutiny, alleging it operates as a "supra-national intelligence organisation" with limited accountability.