The Mouse that Roared is a 1955 novel by Irish writer Leonard Wibberley that launched a series of satirical books about a fictional European nation called the Duchy of Grand Fenwick.

Tiny (3 miles by 5 miles) Grand Fenwick borders Switzerland and France in the Alps, and proudly retains a pre-industrial economy, dependent almost entirely on making Pinot Grand Fenwick wine. Wibberly places Grand Fenwick in a series of absurd situations, where it goes up against superpowers and wins. In The Mouse that Roared it defeats the United States in a war by capturing a super bomb.

In this novels and others, Wibberley goes beyond the merely comic, using the situations to make commentary about modern politics and world situations.

The Mouse That Roared was made into a 1959 film starring Peter Sellers in three different roles (including the Duchess), Jean Seberg as his love interest, and co-starring William Hartnell as Will Buckley.

This film echoes Dr. Strangelove both in Sellers' multiple roles and its satirization of Cold War concepts such as Marshall Plan and paranoia.