Buffy the Vampire Slayer is an American supernatural drama television series created by Joss Whedon. The show's concept is based on the 1992 film, also written by Whedon, although they are separate and distinct productions. Whedon served as executive producer and showrunner of the series under his production tag Mutant Enemy Productions. It aired on The WB from March 10, 1997, to May 22, 2001, and later on UPN from October 2, 2001, to May 20, 2003.

The series follows Buffy Summers (played by Sarah Michelle Gellar), the latest in a succession of young women known as "Vampire Slayers". Slayers are chosen by fate to battle against vampires, demons and other forces of darkness. Buffy wants to live a normal life, but learns to embrace her destiny as the series progresses. Like previous Slayers, she is aided by a Watcher, part of the Watcher's Council based in England, who guides, teaches and trains her. Unlike her predecessors, Buffy surrounds herself with loyal friends who become known as the "Scoobies". The show primarily takes place in the fictional setting of Sunnydale, a small Southern California city located on a "Hellmouth"; a portal "between this reality and the next", and a convergence point of mystical energies. Because of this, supernatural creatures and beings with magical powers, both good and evil, are drawn to Sunnydale or rise from below ground to menace the town and the world.

The series received critical and popular acclaim, and is often listed among the greatest television series of all time. Original airings often reached four to six million viewers. Although lower than successful shows on the "big four" networks (ABC, CBS, NBC and Fox), these ratings were a success for the relatively new and smaller WB Television Network. Despite being mostly ignored in above-the-line categories by the Emmys, the series was nominated for the American Film Institute Award for Drama Series of the Year, Gellar was nominated for the Golden Globe Award for Best Actress – Television Series Drama for her performance in the show and the series was nominated five times for Television Critics Association Awards, winning in 2003 for the Television Critics Association Heritage Award.

The success of Buffy has led to hundreds of tie-in products, including novels, comics and video games. The series has received attention in fandom (including fan films), parody, and academia, and has influenced the direction of other television series. Buffy was part of a wave of television series from the late 1990s and early 2000s that featured strong female characters, alongside Charmed, Xena: Warrior Princess, La Femme Nikita, Dark Angel, and Alias. The series, as well as its spin-off series, Angel, and extensions thereof, have been collectively termed the "Buffyverse".

Buffy Summers (played by Sarah Michelle Gellar) is the "Slayer", one in a long line of young women chosen by fate to battle evil forces. This mystical calling grants her powers that dramatically increase physical strength, endurance, agility, accelerated healing, intuition, and a limited degree of precognition, usually in the form of prophetic dreams. She is known as a reluctant hero who wants to live a normal life. However, she learns to embrace her destiny as the vampire slayer.

Buffy receives guidance from her Watcher, Rupert Giles (Anthony Stewart Head). Giles, rarely referred to by his first name (it is later revealed that in his rebellious younger days he went by "Ripper"), is a member of the Watchers' Council, whose job is to train and guide the Slayers. Giles researches the supernatural creatures that Buffy must face, offers insights into their origins, advice on how to defeat them, and helps her train to stay in fighting form.

Buffy also receives help from the friends she meets at Sunnydale High School: Willow Rosenberg (Alyson Hannigan) and Xander Harris (Nicholas Brendon). Willow is originally a wallflower who excels at academics, providing a contrast to Buffy's outgoing personality and less-than-stellar educational record. They share the social isolation that comes with being different, and especially from being exceptional young women. As the series progresses, Willow becomes a more assertive character and a powerful witch, and realizes she is a lesbian. In contrast, Xander, with no supernatural abilities, provides comic relief and a grounded perspective. Buffy and Willow are the only characters who appear in all 144 episodes, with Xander appearing in 143.

The cast of characters grew over the course of the series. Buffy first arrives in Sunnydale with her mother, Joyce Summers (Kristine Sutherland), who functions as an anchor of normality in the Summers' lives even after she learns of Buffy's role in the supernatural world ("Becoming, Part Two"). Buffy's younger sister Dawn Summers (Michelle Trachtenberg) is introduced in season five ("Buffy vs. Dracula"). Angel (David Boreanaz), a vampire cursed with a soul, is Buffy's love interest throughout the first three seasons. He leaves Buffy after realizing he will never be able to give her a normal life. He goes on to make amends for his sins and to search for redemption in his own spin-off television series, Angel. He makes several guest appearances in the remaining seasons, and is present in Buffy's final episode.