Newt Scamander is the fictional author of the Hogwarts textbook Fantastic Beasts and Where to Find Them.
The book appears inside J.K. Rowling’s Harry Potter world as a reference work used by Hogwarts students. Its credited author, Newton Artemis Fido “Newt” Scamander, is a magizoologist who researches magical creatures.
Rowling published a real comic-relief companion book under the name Newt Scamander in 2001. The book was presented as a reproduction of Harry’s school copy and included notes attributed to Harry and Ron. Its proceeds supported Comic Relief.
Newt later became the central character of the Fantastic Beasts film series, beginning with the 2016 film Fantastic Beasts and Where to Find Them. Eddie Redmayne played him in the films. The fictional textbook author and the film protagonist are therefore the same wizarding-world character.