Ashenden: Or the British Agent (1928) is a spy novel by W. Somerset Maugham that is often considered one of the first works of modern spy fiction. It's a semi-autobiographical account of Maugham's experiences as a British intelligence officer during World War I. The book is a collection of loosely connected short stories, each focused on a different assignment or aspect of espionage, with the central character, Ashenden, serving as a stand-in for the author.

The novel follows Ashenden, a writer who is recruited by the British intelligence service (often called "the Secret Service" in the story) to serve as an undercover agent during World War I. His tasks take him across Europe, where he engages in espionage, sabotage, and deception. Ashenden is portrayed as a rather detached and cynical character, not particularly suited for the emotional turmoil or heroism of espionage, but rather a professional who carries out his orders with a sense of pragmatic duty.

The stories in Ashenden explore the moral ambiguities of espionage, the nature of loyalty and betrayal, and the psychological toll that working in intelligence can have on an individual. Unlike many spy novels, Maugham's treatment is more reflective and realistic, emphasizing the complex, often mundane aspects of being a secret agent.

Ashenden is often cited as a significant precursor to later spy fiction and influenced writers such as John le Carré and Ian Fleming. Maugham's more nuanced, humanist approach to the genre set it apart from more conventional tales of espionage. The novel was also adapted into several films and a radio series.