The Looking Glass War is a spy novel by John le Carré, published in 1965. The plot concerns a British Intelligence agency known as 'The Department', which had much success running agents against the Nazis during the Second World War but has been resting on its laurels since. The Department seems to expend most of its energies on a bureaucratic turf war with the more professional "Circus".

After evidence comes The Department's way that Soviet Missiles are being emplaced near the West German border, the head of the Department, LeClerc decides to send an agent over the border to discover the truth. The Department reactivates one of their agents, a naturalised Pole known as Fred Leiser. Fred is retrained and infiltrated over the border into East Germany.

Le Carré's most famous character George Smiley does appear in the book but only in a supporting role.

John le Carré has stated that this novel is his most realistic portrayal of the intelligence world as he knew it and that this was one reason for its relative lack of success.

The novel was filmed in 1969, starring Christopher Jones as Leiser, Ralph Richardson as LeClerc and Anthony Hopkins as Avery.