Gideon's Day is the first in a series of police procedural novels by John Creasey writing as J.J. Marric.

Published in 1955, it features a day in the professional life of Detective Superintendent George Gideon of the C.I.D., Scotland Yard.

Superintendent George Gideon is furious when he finds out that one of his detectives has accepted bribes.

Other cases that Gideon deals with during the day include hunting for a child's killer and a jewel thief, solving a series of mail van robberies, and trying to find out who killed an old woman in a sweet-shop.

The movie of the same name by director John Ford is a comedy-melodrama, loosely adapted from the book.