Sirius Black III (1959[6] – 18 June, 1996), also known as Padfoot or Snuffles in his Animagus form, was a pure-blood wizard, the older son of Orion and Walburga Black, as well as the older brother of Regulus by slightly over a year. Although he was the heir of the House of Black, Sirius disagreed with his family's belief in blood purity and defied tradition when he was sorted into Gryffindor instead of Slytherin at Hogwarts School of Witchcraft and Wizardry, which he attended from 1971 to 1978.

As Sirius' relationship with his relatives deteriorated, he gained lifelong friendship in James Potter, Remus Lupin, and Peter Pettigrew. The four friends, also known as the Marauders, joined the Order of the Phoenix to fight against Lord Voldemort and his Death Eaters during the First Wizarding War. Sirius also became the godfather of Harry Potter.

Sirius rejoined the Order. He was murdered by his cousin Bellatrix Lestrange during the Battle of the Department of Mysteries and subsequently cleared of all charges by the Ministry of Magic.