The British-US Communication Intelligence (UKUSA) Agreement was signed by representatives of the London Signals Intelligence Board and its American counterpart in March 1946. The UKUSA Agreement is without parallel in the Western intelligence world and formed the basis for co-operation between the two countries throughout the Cold War.
Today it is is a multilateral agreement for cooperation in signals intelligence among the United Kingdom, the United States, Canada, Australia, and New Zealand. The alliance of intelligence operations is also known as Five Eyes. The agreement established an alliance of five English-speaking countries for the purpose of sharing intelligence, especially signals intelligence.