Marcus Belby was a wizard who attended Hogwarts School of Witchcraft and Wizardry. He was sorted into Ravenclaw House and was described as "thin and nervous-looking". He became a candidate for the Slug Club because his Uncle Damocles invented the Wolfsbane potion.

In the filmsEdit

The role of Marcus in the film adaptation of Harry Potter and the Half-Blood Prince was played by Robert Knox.