Harley Quinn is a fictional character and supervillain appearing in American comic books published by DC Comics. She was created by writer Paul Dini and artist Bruce Timm, making her debut not in a comic book, but in the acclaimed television series Batman: The Animated Series. Her first appearance was in the episode "Joker's Favor," which aired on September 11, 1992. Originally conceived as a one-off henchwoman for the Joker, the character's instant popularity led to her becoming a recurring figure in the DC Animated Universe.
The character's origin story, later fleshed out in comics, reveals her as Dr. Harleen Quinzel, a promising psychiatrist at Arkham Asylum. She becomes fascinated with her patient, the Joker, and is manipulated into falling in love with him, eventually breaking him out and adopting the costumed persona of Harley Quinn. Her name is a playful nod to the Harlequin character from the 16th-century Italian commedia dell'arte. For years, she was defined by her toxic, co-dependent relationship with the Joker, serving as his sidekick and love interest.
Harley Quinn was officially integrated into the mainstream DC Comics universe in 1999 with the one-shot comic Batman: Harley Quinn #1. Over the following decades, she evolved far beyond the Joker's girlfriend. Writers developed her into a more independent anti-hero, exploring her deep friendship and romantic partnership with Poison Ivy, her membership in the Suicide Squad, and her solo adventures as a chaotic force for good (or at least, for herself) in Gotham City's criminal underworld. She has become one of DC's most popular and commercially successful characters, headlining multiple solo comic series and appearing across virtually all media.