The Government of the United Kingdom maintains several intelligence agencies that deal with secret intelligence. These agencies are responsible for collecting, analysing and exploiting foreign and domestic intelligence, providing military intelligence, and performing espionage and counter-espionage. Their intelligence assessments contribute to the conduct of the foreign relations of the United Kingdom, maintaining the national security of the United Kingdom, military planning, public safety, and law enforcement in the United Kingdom. The four main agencies are the Secret Intelligence Service, the Security Service (MI5), the Government Communications Headquarters (GCHQ) and Defence Intelligence (DI). The agencies are organised under three government departments, the Foreign Office, the Home Office and the Ministry of Defence.

The Secret Intelligence Service (SIS), commonly known as MI6, is the foreign intelligence service of the United Kingdom, tasked mainly with the covert overseas collection and analysis of human intelligence on foreign nationals in support of its Five Eyes partners. SIS is one of the British intelligence agencies and the Chief of the Secret Intelligence Service ("C") is directly accountable to the Foreign Secretary.