Dr. Harleen Quinzel, better known as Harley Quinn, is the secondary antagonist of the Batman: Arkham franchise, appearing as one of the secondary antagonists (alongside Poison Ivy) of the 2009 videogame Batman: Arkham Asylum and a supporting antagonist in its 2011 sequel videogame Batman: Arkham City. She also appears as one of the major antagonists in the 2015 sequel videogame Batman: Arkham Knight, the secondary antagonist of its prequel DLC episode Batgirl: A Matter of Family, and the eponymous titular main antagonist of the Batman: Arkham City sequel DLC episode: Harley Quinn's Revenge.

She was the Joker's former henchwoman, girlfriend. and staple sidekick to the Joker in all forms of Batman media (although Joker was highly abusive, she remains largely the same and this did not stop Harley from later seeking revenge after his death). After Joker's illness and death, Harley takes over his gang along with many of his other responsibilities.  

She is voiced by Arleen Sorkin in Arkham Asylum, Tara Strong in Arkham City, Arkham Origins, and Arkham Knight, and by Hynden Walch in Batman: Assault on Arkham.

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