The Once and Future King is a work by T. H. White based upon Le Morte d'Arthur by Sir Thomas Malory. It was first published in 1958. It collects and revises shorter novels published from 1938 to 1940, with much new material.
Most of the book takes place in "Gramarye", the name White gives to Britain, and chronicles the youth and education of King Arthur, his rule as a king, and the romance between Sir Lancelot and Queen Guinevere. Though Arthur, if he existed at all, would have ruled some time around the 6th century, the book is set around the 14th century (and Arthur is portrayed as an Anglo-Norman rather than a Briton), and the actual monarchs of that period are referred to as "mythical". The book ends immediately before Arthur's final battle against his illegitimate son Mordred. Though White admits his book's source material is loosely derived from Le Morte d'Arthur, he reinterprets the epic events, filling them with renewed meaning for a world recovering from World War II.