The Duchy of Grand Fenwick is a tiny fictional country created by Leonard Wibberley in a series of comedic novels beginning with The Mouse That Roared (1955), which was later made into a film.
The duchy, ruled by Grand Duchess Gloriana XII, is described as bordering Switzerland and France in the Alps. It retains a pre-industrial economy, dependent almost entirely on making Pinot Grand Fenwick wine. It takes its name from its founder, the English knight Sir Roger Fenwick, who, while under the employ of the French, settled there with his followers in 1370. (The story of Sir Roger's conquest of the duchy is told in Wibberly's 1958 book, Beware of the Mouse.) Thanks to Sir Roger, the national language is English.In the novels, Wibberley goes beyond the merely comic, placing the tiny nation (15 square miles /39 square kilometers) in absurd situations so as to comment on then-contemporary politics and events.
In The Mouse That Roared, for example, the duchy seeks to stop American counterfeiting of Pinot Grand Fenwick. Grand Fenwick's formal protests are ignored by U.S. State Department employees, who think the documents are pranks. Grand Fenwick then plans an attack on the United States, certain this will lead to immediate defeat followed by generous American aid. The duchy's forces, clad in chain mail and armed with longbows, arrive in New York during an air raid drill and can find no one to surrender to. Ultimately they take prisoners and return to Grand Fenwick. One captive is the inventor of the Q-bomb, and the duchy finds itself the possessor of the only working model of this devastating weapon. Grand Fenwick forms an alliance of small nations, the Tiny Twenty, and uses its control of the bomb to obtain world peace.
In The Mouse on the Moon (1962), Grand Fenwick beats the U.S. and Soviet Union in a space race by using a new rocket fuel, the secret ingredient for which is a "premier grand cru" crop of Pinot Grand Fenwick.
In The Mouse on Wall Street (1969), the duchy disrupts the world's finances.
Grand Duchess Gloriana: How did the war go?
Tulley Bascombe: Well, this is a bit of a surprise. A pleasant one, I hope. I think we've won.