Who Are You? (Buffy the Vampire Slayer)

"Who Are You?" is the sixteenth episode of the fourth season of the American supernatural drama television series Buffy the Vampire Slayer. It was written and directed by series creator Joss Whedon and originally aired on The WB on February 29, 2000.

In the series, Buffy Summers (Sarah Michelle Gellar) is a Slayer, a teenage girl endowed with superhuman powers to fight evil forces. "Who Are You?" is the second half of a two-part story arc featuring the return of the rogue Slayer Faith (Eliza Dushku) and is a turning point in the character's redemptive arc. The previous episode saw Faith use a magical device to swap bodies with Buffy, and Whedon wanted to use this premise to explore Faith's psyche and give her a moral epiphany. In Buffy's body, Faith experiences love and acceptance from others and realizes how unhappy her own life is. Initially dismissive of Buffy's morality, Faith also comes to appreciate a Slayer's duty to protect others. Whedon used the phrase "Because it's wrong", said by Faith mockingly at first but with full conviction by the end, to convey her psychological transformation. The body swap premise meant that Gellar played Faith and Dushku played Buffy for much of the episode.

"Who Are You?" was watched by 4.9 million viewers. Academic analysis has focused on its commentary about morality and identity. The episode has featured highly on some retrospective Buffy rankings. Often regarded as some of the best acting of the series, critics were impressed with the way Gellar and Dushku adapted their physical and verbal mannerisms in their performances as each other's characters.