The Mouse That Roared
The Mouse That Roared is a 1955 Cold War satirical play based on the novel by Irish-American writer Leonard Wibberley, which launched a series of satirical books about an imaginary country in Europe called the Duchy of Grand Fenwick. Wibberley went beyond the merely comic, using the premise to make still-quoted commentaries about modern politics and world situations.

Released in February 1955 by Little, Brown, the novel first appeared under the title The Day New York Was Invaded as a Saturday Evening Post serial in six consecutive weeks, from Christmas Day, 1954, through 29 January 1955. The English edition (London: Robert Hale, 1955) had the author's original title, "The Wrath of Grapes", a play on John Steinbeck's The Grapes of Wrath.

The playtakes a satirical look at themes including the nuclear arms race, nuclear weapons in general, and the politics of the United States. The phrase "mouse that roared" has proved a durable meme.