The Secret Intelligence Service (SIS), commonly known as MI6, (Military Intelligence, Section 6) is the agency which supplies Her Majesty's Government with foreign intelligence. It operates under the formal direction of the Joint Intelligence Committee (JIC) alongside the internal Security Service (MI5), the Government Communications Headquarters (GCHQ) and the Defence Intelligence (DI).

It is frequently referred to by the name MI6 (Military Intelligence, Section 6), a name used as a flag of convenience during the Second World War when it was known by many names. The existence of MI6 was not officially acknowledged until 1994.

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