A killer toy or a killer doll is a stock character in horror fiction and urban legends. They include toys, such as dolls and ventriloquist dummies, that come to life and seek to kill or otherwise carry out violence. The killer toy subverts the associations of childhood with innocence and lack of agency while invoking the uncanny nature of a lifelike toy. Killer toy fiction often invokes ideas of companionship and the corruption of children, sometimes taking place in dysfunctional or single parent homes. They have historically been associated with occultism and spirit possession, though artificial intelligence became more common in later works.

The killer toy most commonly appears in film, where it dates back to Dead of Night (1945) and expands on earlier films such as The Great Gabbo (1929) and The Devil-Doll (1936). These early examples primarily featured ventriloquist dummies, with works featuring killer dolls developing in the 1960s through the 1980s. The genre of killer toy fiction was popularized by Child's Play (1988) and its killer doll Chucky, which has become widely recognized as a horror icon in popular culture. Killer toy fiction has remained prevalent in horror, and other popular killer doll franchises have been created since then, including Puppet Master and The Conjuring.

Nineteenth-century precursors to the killer toy include "The Sandman" (1816) by E. T. A. Hoffmann and The Adventures of Pinocchio (1883) by Carlo Collodi, both of which experimented with the idea of a puppet's identity becoming more humanlike. Many American children's stories in the late 19th century emphasized dolls, sometimes marketing themselves as being written by the doll. These stories acknowledged the bond between children and dolls and the personification of dolls by children, both of which would be subverted by later killer-toy fiction.

Ventriloquist dummies served as some of the earliest examples of unnatural toys in horror films, being established with "Otto" in the musical drama The Great Gabbo (1929). The dummy was a convenient prop for early film, as it could largely be operated onscreen without any technical special effects. Dead of Night (1945) is the first identified example of a killer dummy in film, establishing its dummy Hugo by building on the ideas in The Great Gabbo. The killer dummy became a stock character in horror over the following decades, with appearances in The Dummy Talks (1943), Alfred Hitchcock Presents (1957), The Twilight Zone (1962 and 1964), and Magic (1978). The relationship between the ventriloquist and the dummy influenced later killer toy characters, even as they moved away from strictly psychological elements toward the supernatural.

The Devil-Doll (1936) developed a predecessor to the killer doll, featuring shrunken humans controlled psychokinetically. The Twilight Zone introduced Talky Tina, one of the first on-screen killer dolls, in the episode "Living Doll" (1963). This use of the killer doll was contrasted with the idea of a dysfunctional family, with the narrator describing the doll as the child's "guardian". This portrayal was inspired by the advent of talking dolls like Chatty Cathy in the 1960s, which allowed for increased characterization and uncanniness of killer toys.

In the 1960s, the trend of ugly and "monstrous" toys began, with toy manufacturers such as Aurora Plastics Corporation expanding from traditional dolls and toys that complied with conceptions of morality at the time. These toys included merchandising based on popular monster movies as well as other "unattractive" toys such as toy insects. By the 1970s, this trend became associated with counterculture and teenage rebellion, incorporating imagery that would go on to be associated with horror fiction and goth subculture.

Poltergeist (1982) portrayed a killer toy with an evil clown toy that was possessed while in a supernatural realm. The film demonstrated the clown's agency by having it move while offscreen before having the child establish his own agency by killing the clown toy in self-defense. Dolls (1987) introduced the concept of explicitly creating horror through the imagery of childhood manifested by dolls.

The development of animatronics allowed for more sophisticated killer toy characters beginning in the 1980s. The film Child's Play (1988) popularized killer toy films and established its killer doll, Chucky, as a defining example of the killer doll in popular culture. This incarnation of the killer doll incorporated many of the ideas that defined such characters, including the subversion of childhood innocence, the share of agency between the toy and a child, and the emergence of the occult into the living world. The film was distinct in the source of its killer toy; rather than an undefined demonic presence, the character of Chucky is created in the physical world from a previously established character. Child's Play defined the genre, inspiring numerous successors and other similar films. Killer doll films proliferated over the following years, including further Child's Play films, the Puppet Master film series, Dolly Dearest (1991), and Pinocchio's Revenge (1996).