Junko Enoshima (Japanese: 江ノ島 盾子, Hepburn: Enoshima Junko) is a fictional character and the overarching antagonist of Spike Chunsoft's Danganronpa series. She is introduced as the mastermind behind the first two games and the true persona of the series mascot Monokuma. In the spin-off game Danganronpa Another Episode: Ultra Despair Girls, she appears via the avatars of Shirokuma and Kurokuma. Junko also serves as the protagonist of the prequel light novel Danganronpa Zero under the identity of the Ultimate Analyst, Ryōko Otonashi (Japanese: 音無 涼子, Hepburn: Otonashi Ryōko) and further appears in the anime Danganronpa 3: The End of Hope's Peak High School: Despair Arc.

A student of Hope's Peak Academy, Junko is the Ultimate Fashionista, a charismatic and hyper-intelligent gyaru fashion model. Alongside her fraternal twin sister and body double Mukuro Ikusaba, she forms the Ultimate Despair, and orchestrates the end of civilization through a movement known as "The Tragedy". In Danganronpa: Trigger Happy Havoc, Junko arranges a killing game between her former classmates to test their metrics for hope and despair, participating alongside Mukuro as "hidden" contestants. Following her death, Junko's consciousness is preserved into an artificial intelligence known as Alter Ego Junko. This AI serves as a central antagonist in Danganronpa 2: Goodbye Despair and Danganronpa Another Episode: Ultra Despair Girls, where she works with Izuru Kamukura to ensure the continuation of her plans.

The identity of Junko is frequently adopted by other characters throughout the franchise. Mukuro Ikusaba poses as her sister in Danganronpa: Trigger Happy Havoc and Danganronpa Zero, while an intended successor seeks to claim her mantle in Danganronpa Another Episode: Ultra Despair Girls. Additionally, the showrunners of the Danganronpa reality television series utilize her likeness in Danganronpa V3: Killing Harmony. The character has also appeared in various manga and musical adaptations of the series.

Junko was conceived by series' creator and scenario writer Kazutaka Kodaka originally as a "fully unsympathetic" villain, due to his at the time personal dislike for the popular trope of being a sympathetic villain. Kodaka later elaborated that Junko appears to have toxic love towards her classmates due to how rather than killing them, she forces them to kill each other as she believes that despair is the ultimate salvation for people.

"I wanted to create a character who is bad because she is evil, who only desires outright desperation. With no possibility of redemption ... Another thing I wanted to do was create a really cute character who was evil. Also that she had the idea that absolute evil is something desirable and pleasant. As bad as she is, she is so powerful and charming that she draws you in. So one way I thought of showing that was to make a very cute character that was visually appealing to look at." — Kazutaka Kodaka

Kodaka later confirmed Junko's motives to be rooted in her obsession for the entirety of her classmates, seeking to induce more despair on someone and herself the more they meant to them, along with subtle hints of her past and sanity slippage. Early concept art for the character depicts her with smaller pigtails, a white skirt, and an overall golden color scheme with red and black highlights, elements of which were also adopted for the character's fraternal twin sister Mukuro Ikusaba. The character's resurrection in Goodbye Despair was left to the player's interpretation. Kodaka compared the theory of whether or not she is dead or alive to Western villains like the Joker who are continuously brought back to life. However, Kodaka claims Junko can be killed. In retrospective, he feels like Junko could be his strongest villain ever created. Due to how powerless Junko is in comparison to Izuru, the scenes involving how the former manipulates the latter were written to show Junko at her lowest since she could not defeat Izuru in combat, so the writers focused on psychology involving their passions.

In the first game, Danganronpa: Trigger Happy Havoc, Junko fakes her death by having Mukuro pose as her so she can kill her under her Monokuma guise, using the event to encourage her former classmates at Hope's Peak Academy to participate in a "killing game", both actions serving to feed her desire to fuel an "ultimate despair" within herself and them. Throughout the game, Junko (in the form of a robotic teddy bear dubbed Monokuma) provides various motives to turn the students against one another, overseeing the subsequent class trials and performing the various executions while broadcasting the events to the world at large, culminating in her presenting Mukuro's corpse in an attempt to frame the "Ultimate Detective" Kyoko Kirigiri without breaking the rules she set for herself for the "killing game", and ultimately agreeing to execute herself after being exposed as the mastermind.

In Danganronpa 2: Goodbye Despair, Junko is revealed to have used Chihiro's Alter Ego technology to transfer her consciousness into Monokuma at the moment of her death as an A.I. (explaining their reactivation in the prior game's post-credits scene), hijacking the Future Foundation's attempted removal of her followers' brainwashing by having the former "Ultimate Hope" Izuru Kamukura download her into their rehabilitation program "Neo World", where she places their younger virtual selves into another "killing game". In the game's climax, Junko's true plan is assumed to be to transfer her A.I self into the bodies of those of her followers whose virtual selves killed each other, their real selves having arranged their capture to allow Junko a chance to return in a physical body, and from there to the watching Future Foundation and the wider world at large, to be dubbed "Junkoland". Ultimately, after her still-living followers' virtual selves decide to remain in the program, Alter Ego Junko is deleted by a new manifestation of the program's former operator, Usami.