Spy is a British television programme originally made by Wall to Wall for BBC Three in 2004. It has been one of the most-exported United Kingdom television shows of the present decade; according to the Producers' Alliance for Cinema and Television, it had been sold to 129 countries by April 2005.

The series follows a group of real-life volunteers as they are trained by former spies in espionage techniques, including maintaining a false identity, surveillance, persuasion and recruitment. The programme's psychological challenges, dramatic tension, high production values, and personable cast led to its being called 'the most addictive thing on TV at the moment' by The Daily Telegraph.

The series further develops a format that first appeared in the Wall to Wall television productions Spymaster and Spymaster USA.

SPY: A Handbook, a companion book written by Harry Ferguson, a trainer featured on the show, was published in 2004 by Bloomsbury in the UK.