Newt Scamander is the fictional author of the Hogwarts textbook Fantastic Beasts and Where to Find Them.
Rowling published Fantastic Beasts and Where to Find Them in 2001 as a companion book connected with the Harry Potter world. In the fictional framing, the book is a Hogwarts textbook written by Newt Scamander. Harry, Ron, and Hermione are presented as former owners of a school copy.
Newt later became the central character of the Fantastic Beasts film series, beginning with Fantastic Beasts and Where to Find Them in 2016. Eddie Redmayne portrays him in the films. The character is a magizoologist, a specialist in magical creatures.
Newt is not the same person as the textbook’s real-world credited author, J.K. Rowling. Scamander is an in-universe author, while Rowling created and wrote the companion publication and later screenplay.