Severus Snape is a fictional character in J. K. Rowling's Harry Potter series. He is characterised as a person of great complexity, whose coldly sarcastic and controlled exterior conceals deep emotions and anguish. In the first novel of the series, Snape is a teacher who is hostile from the start toward Harry. As the series progresses, Snape's character becomes more layered and enigmatic. Rowling does not fully reveal the details of his true loyalties until the end of the final book, Harry Potter and the Deathly Hallows. Over the course of the series, Snape's portrayal evolves from that of a malicious and partisan teacher to that of a pivotal character of considerable intricacy and moral ambiguity.

In the series, Snape is an exceptionally skilful wizard who primarily teaches Potions at Hogwarts school. In the sixth novel, he teaches Defence Against the Dark Arts, a position which he was known to have desired throughout the series. For much of the series, Snape's actions seem to serve Harry's nemesis, Lord Voldemort, although Harry's mentor, Dumbledore, often advises Harry that – despite his actions and animosity – Snape is trustworthy and his true loyalties can be relied upon. He ultimately becomes Headmaster of Hogwarts in the final novel, after killing Dumbledore at the end of the sixth book. Snape himself dies at the hands of Voldemort in the final chapters of the seventh book, revealing his memories and true back story to Harry (and therefore to the reader) in his last minutes: Snape was a childhood friend of Harry's mother, Lily, and swore to protect Harry because of a deep and unending love for her. In the book's epilogue, Harry describes Snape as "probably the bravest man I ever knew".

The character was widely acclaimed by readers and critics; Rowling described him as "a gift of a character"[1] whose story she had known since the first book. Actor Alan Rickman portrayed Snape in all eight Harry Potter films, released between 2001 and 2011.