Professor Severus Snape (9 January, 1960 – 2 May, 1998) was an English half-blood wizard serving as Potions Master (1981-1996), Head of Slytherin House (1981-1997), Defence Against the Dark Arts professor (1996-1997), and Headmaster (1997-1998) of the Hogwarts School of Witchcraft and Wizardry as well as a member of the Order of the Phoenix and a Death Eater. His double life played an extremely important role in both of the Wizarding Wars against Voldemort.

Snape later participated in the Battle of Hogwarts but was murdered by Lord Voldemort who mistakenly believed that Snape was the master of the Elder Wand (an immensely strong and powerful wand that Voldemort deeply desired, as well as one of the Deathly Hallows) when in reality, Harry Potter was the master of the Elder Wand, because Draco Malfoy had disarmed Dumbledore on the night of Dumbledore's death on top of the Astronomy Tower, and Harry had disarmed Draco at Malfoy Manor.

After Snape's death, Harry Potter ensured that his portrait remained at Hogwarts, honouring him as a hero, despite their significant personal differences. In addition, Harry later named his second son Albus Severus Potter in honour of Dumbledore and Severus, both of whom were an inspiration in Harry's life after the Battle of Hogwarts. Harry also was influenced by Severus' Hogwarts house, and freely admitted that his son Albus could choose Slytherin if he wished.