Joyce Summers is a fictional character in the action-horror television series Buffy the Vampire Slayer (1997–2003). Played by Kristine Sutherland, Joyce is the mother of the main character, Buffy Summers, and appears in 58 of the 144 episodes.

The premise of the series is that Buffy is the latest Slayer, a young woman endowed by mystical forces with superhuman powers to fight and defeat vampires, demons, and other evil forces in the fictional town of Sunnydale. Like every Slayer before her, she was chosen and informed of her destiny when she was 15 years old. Her mother is unaware of her daughter's powers and responsibilities until Buffy is forced to tell her at the end of the second season of the television series. Although Joyce is shocked at this revelation, she recovers quickly and remains a source of stability for Buffy and Buffy's small circle of friends who assist her, dubbed the Scooby Gang. Eventually Joyce is able to take Buffy's dangerous demon-fighting in stride and even become proud and respectful of her daughter's abilities. Her natural death from an illness in the fifth season forces Buffy to face becoming an adult.

The television series Buffy the Vampire Slayer (often simplified as Buffy) was created by Joss Whedon, who originally used the concept of a teenage girl who is given superhuman powers to fight evil, in a screenplay that became a film in 1992. Unhappy with the outcome of the film, Whedon created the series, which picks up shortly after the events of the film and is loosely based on its ending. At the end of the film, which was set in Los Angeles, Buffy fights and defeats a gang of vampires in her school's gymnasium. At the start of the television series Buffy and her mother Joyce, who has divorced Buffy's father, move to a new town named Sunnydale where Buffy is to attend Sunnydale High School, which, unknown to her, is situated on a portal to hell, called a Hellmouth. The series explains that she has relocated from Los Angeles after burning down the gymnasium, marking her as a trouble-making student and a worrisome daughter. The series regularly employs the elements of dark fantasy and horror to represent the real problems regularly encountered by adolescents, with many situations also reflecting adult fears and anxieties.

Buffy's parents are barely seen in the film, but her mother Joyce (Kristine Sutherland) plays a prominent role in the series. Sutherland, a fantasy fiction fan who dislikes the horror genre, had recently moved to Hollywood from New York City in 1996 and was not actively looking for acting jobs when her agent called her with the opportunity to play Joyce. Sutherland auditioned the same day as David Boreanaz, Buffy's romantic interest Angel, and was impressed with how naturally she felt at ease with the material in the readings with the writers and casting agents. Sutherland said in an interview that she felt she identified strongly with adolescents. Her empathy for them made her protective not only of the actors, but of their characters as well. A storyline with the premise that Joyce be possessed as the mother from hell was one of Sutherland's favorite possible scripts, but it was cut.

Buffy is introduced to her new school as a student who is both emotionally and academically troubled. With the move to Sunnydale, she believes she is starting fresh, a notion her mother also believes and encourages. As Buffy establishes herself in school in early episodes, Joyce, who is recently divorced, is preoccupied with setting up their home and running an art gallery. Initially unwilling to become involved again with her role as the Slayer, Buffy is nevertheless confronted by the school librarian Giles (Anthony Head), her new Watcher, the mentor and teacher assigned to instruct her how to fight vampires and other demons she is destined to face. Buffy does not tell her mother about this development, and Joyce remains ignorant of Buffy's role as the Slayer and of Giles' influence in her life, something she later resents when he seems to be closer to Buffy in ways Joyce is not.

Joyce's initial role in the series is, according to scholar J. P. Williams, very similar to the Superman character Lois Lane, who is unable to discern the likeness between Clark Kent with his glasses on and Superman with his glasses off. Buffy is frequently referred to as a superhero by authors, and Joyce's initial ignorance of Buffy's abilities and responsibilities creates skepticism among both characters in the series and viewers about Joyce's intelligence and motivations. For example, Joyce sees the extremely attentive Giles merely as a teacher concerned about Buffy as a student who has experienced academic problems in the past.

This willful ignorance of Buffy's vocation has been well-analyzed by Buffy studies scholars. A persistent theme in Buffy is the nearly unbreachable generation gap between adolescents and adults. Throughout the series, adults are either unable or unwilling to see the genuine horrors teenagers face. As Buffy's mother, Joyce is repeatedly confronted with evidence of her daughter's role as the Slayer; Sutherland saw this as a form of denial on Joyce's part. The resulting conflict between Joyce and Buffy is both tragic and humorous. When Buffy skips class or stays out late to attend to her Slayer duties, Joyce is left trying to punish her by restricting her to the house. Joyce responds to the dire situations Buffy must face by placing regular and inconvenient restrictions on her, such as grounding her at a time when Buffy must confront and try to kill the Master (the head of a vampire cult who is attempting to fulfill a prophecy that he will kill the Slayer and open the Hellmouth in Sunnydale), saying sarcastically to Buffy, "I know—if you don't go out it'll be the end of the world", when in fact, it just may be, or telling Buffy that she is free to make her own life choices, when Buffy knows exactly what her destiny is, and that it may include dying young. This duality of language reinforces the generation gap between the characters.

That the way I as Joyce see Buffy as the Slayer is sort of symbolic, when you look at your child and realize they are a totally different person than you are and that they have different gifts and a different calling. It's a separation thing. In this case it's just more extreme and because it isn't just that she's an incredible pianist. It's something that has a moral cause behind it and so it brings dual feelings. 'I'm your mother and I'm older and I'm wiser but yet you're my daughter and you're this really spectacular person who's going places and wrestling with things that are beyond what I'll ever have to do in my lifetime.'