Quiller is a fictional character created by English novelist Elleston Trevor. Quiller, whose one-word name is a pseudonym, works as a spy, and he is the hero of a series of Cold War thrillers written under the pseudonym "Adam Hall".
The books focus on a solitary, highly capable operative who works, usually on his own, for a British government organization, referred to as "The Bureau", which "doesn't exist". Quiller narrates his adventures in first person, addressing the reader in an informal tone. He was named for the real-life Cornish writer Sir Arthur Quiller-Couch.