Alexander Lavelle "Xander" Harris is a fictional character created for the action-horror/fantasy television series Buffy the Vampire Slayer (1997–2003). He was developed by Joss Whedon and portrayed throughout the television series by Nicholas Brendon and in two episodes by his twin brother, Kelly Donovan. He was conceived as an everyman and a male character for series heroine Buffy Summers (Sarah Michelle Gellar) to interact with, and to provide comic relief in the series. Xander is one of several friends of Buffy who assist her in saving the world against numerous supernatural events that plague Sunnydale, California, a town built over a doorway to hell.

Xander is based in part on Whedon himself, particularly in his high school years; as such, he is often the most geeky as well as witty and verbose of Buffy's characters. The character's overriding arc through the series has been his struggle towards maturity and earning the respect of others. In the canonical comic book continuation of the series, Buffy the Vampire Slayer Season Eight (2007–2011), Xander comes to achieve these goals in becoming the tactical leader of a global army of Vampire Slayers alongside Buffy.