Sirius Black is a fictional character in J. K. Rowling's Harry Potter series. Sirius was first mentioned briefly in Harry Potter and the Philosopher's Stone as a wizard who lent Rubeus Hagrid a flying motorbike shortly after Lord Voldemort killed James and Lily Potter. His character becomes prominent in Harry Potter and the Prisoner of Azkaban, in which he is the titular prisoner, and is also revealed to be the godfather of the central character Harry Potter. He is portrayed in the film adaptations by Gary Oldman.

Harry Potter is a series of seven fantasy novels written by British author J. K. Rowling. The novels chronicle the lives of a young wizard, Harry Potter, and his friends Hermione Granger and Ron Weasley, all of whom are students at Hogwarts School of Witchcraft and Wizardry. The main story arc concerns Harry's conflict with Lord Voldemort, a dark wizard who intends to become immortal, overthrow the wizard governing body known as the Ministry of Magic, and subjugate all wizards and Muggles.