One True King is a 2020 fairytale fantasy by Soman Chainani. The final novel of The School for Good and Evil series and set after the events of A Crystal of Time, the book details Tedros', son of King Arthur, fight to become King of Camelot and prevent Japeth, who is impersonating his brother, from becoming the "One True King".

Soman Chainani is an American author and filmmaker, best known for writing the children's book series The School for Good and Evil.