The Will of an Eccentric (French: Le Testament d'un excentrique) is a 1900 adventure novel written by Jules Verne based on the Game of the Goose.

William J. Hypperbone, an eccentric millionaire, living in Chicago, has left the sum of his fortune, $60,000,000, to the first person to reach the end of "The Noble Game of the United States of America."

The contestants are Max Réal, with his companion Tommy; Tom Crabbe, with his trainer John Milner; Hermann Titbury, with his wife Kate; Harris T. Kymbale (on his own); Lizzie Wag, with her friend Jovita Foley; Hodge Urrican, with his companion Turk; and the mysterious player only known as "XKZ."

Who is this mysterious "XKZ" who was added to the game by a codicil to the will?

In 1897, the first Baedecker guidebook for the U.S. was published, and Verne used this as the source for his descriptions of the modes of transport, timetables, and geographic descriptions of the numerous places the twelve participants were required to visit in order to claim the prize.