The Looking Glass War is a 1965 spy novel by John le Carré. Written in response to the positive public reaction to his previous novel, The Spy Who Came in from the Cold, the book explores the unglamorous nature of espionage and the danger of nostalgia. The book tells the story of an incompetent British military intelligence agency known as The Department and its multiple botched attempts to verify a Communist defector's story of a Soviet missile buildup in East Germany. Some editions hyphenate "Looking Glass".

David John Moore Cornwell, better known by his pen name John le Carré, was a British author, best known for his espionage novels, many of which were successfully adapted for film or television. A "sophisticated, morally ambiguous writer", he is considered one of the greatest novelists of the postwar era. During the 1950s and 1960s, he worked for both the Security Service (MI5) and the Secret Intelligence Service (MI6). Near the end of his life, due to his strong disapproval of Brexit, he took out Irish citizenship, which was possible due to his having an Irish grandparent.