The Junior Ganymede Club is a recurring fictional location in the Jeeves stories of British comic writer P. G. Wodehouse, being a London club for "gentlemen's gentlemen", i.e. valets, especially for those whose employers are members of the Drones Club. Bertie Wooster's valet Jeeves is a member of the club. It is located in Curzon Street in Mayfair.
The club's name comes from Ganymede, who was the cup-bearer of Zeus.
One of the club's rules states that its members are required to enter any embarrassing or compromising information about their employers into the Junior Ganymede Club Book, and it is much laughed about among the members that the section entitled WOOSTER B is the largest, containing eleven pages at the time the book is first mentioned in the stories, but having expanded to eighteen by the time of Much Obliged, Jeeves. While the rule requires that members keep the information recorded in the book strictly confidential, Jeeves uses it on occasion to help his employer, most notably to discover the nature of Roderick Spode's business in The Code of the Woosters.
In Much Obliged, Jeeves, Brinkley (or Bingley) a former valet of Bertie's friend Ginger Winship, steals the Club Book and threatens to sell it, endangering Winship's campaign for election to the British House of Commons; however, Jeeves promptly recovers it by drugging Brinkley/Bingley's drink. Later, Bertie manages to persuade Jeeves to remove the section detailing his own exploits, to guard against any possibility that the book might be stolen in the future.