Young adult fantasy (YA fantasy) brings together two established genres - young adult fiction and fantasy fiction - and in so doing amplifies, energises, and leverages the textual, social, and industrial practices of the two genres: combining the fantastic with adolescent concerns; engaging passionate online fandoms; proliferating quickly into series and related works. By considering the texts alongside the way they are circulated and marketed, this Element aims to show that the YA fantasy genre is a dynamic formation that takes shape and reshapes itself responsively in a continuing process over time.