*Harley Quinn (aka Dr. Harleen Frances Quinzel), is the titular main protagonist of the animated Harley Quinn franchise.

Harley is the former girlfriend and sidekick of The Joker and is currently dating her best friend Poison Ivy. Since breaking up with Joker, she has led and founded a ragtag crew of villainous misfits and briefly became a member of the Legion of Doom. At the end of season 3, Harley realizes she does not feel like a villain anymore and decides to join the Bat Family as a crime fighter. At the end of season 4, Harley ultimately realizes the fact that she is more of an Anti-Hero and thus leaves the Bat-family, later joining the newly created Gotham City Sirens. However, due to the teammates' inability to work together they disbanded before the events of season 5.

Harley Quinn is a tall and slim Caucasian young adult woman with bleached white skin and blue eyes. Harley has an athletic rectangle body type from her past as an acrobat. She has long blonde hair, usually in a pigtails style, which is dyed at the ends in blue and pink shades. She occasionally wears it down when she dresses up, such as during the Legion of Doom party. Harley's makeup usually wears dark red lipstick, pink and blue eyeshadow, black mascara and eyeliner as part of her makeup, and a demonic grin whenever she's ready to fight.

Harley's regular outfit is a skintight short black and red strapped rubber/latex cropped tank top with a star and diamond on it, a black metal choker around her neck, black and red fingerless leather gloves, black and red skintight rubber/latex briefs, long black and red thigh-high stockings with a red stripe on top and diamond on the black stocking plus a black stripe on top and star on the red stocking, and black and red sneakers with pompoms. Underneath Harley Quinn's common shoes, they usually appear as plain white soles, but they also have the red and black footstep pattern in which a red star is on the black and the black diamond is on the red. Occasionally, they also appear with blank red and black soles. In the cold on Catwoman, and Thawing Hearts, she adds a black and red jacket — also with diamonds and a star pattern — to keep herself warm; she also wears this jacket to conceal explosives in The Final Joke.

At the end of season 4, following the discovery that she was the one who killed Nightwing, Harley doubts if she can be a crimefighter alongside the Bat Family, thinking that in the end, she's a villain at her core, so she decides to quit the Bat Family. After Barbara is shot by Joker, Harley goes for revenge, breaking into Bethany's House, kidnapping and torturing Joker to avenge her friend. When Joker asks Harley if she's good or bad, she only responds that she's "in the middle", but is not entirely sure. Later, while attending Lex Luthor's birthday party on the moon to help Ivy in her plan to kill Luthor, thanks to the support of her girlfriend, she realizes she is neither good nor bad, but instead, in the middle is "in the outside", capable of doing heroic actions while using her traits as a villain, something she demonstrates by being worried at the people of the buildings Ivy wants to destroy but being fine with those actions, and also saving Superman after seeing he was kidnapped and used as a lab rat by Luthor leaving him on a deteriorated state, while they were destroying Luthor's base on the moon. After this, she concludes she is more than just the labels of "hero" or "villain", and instead she's "Harley Quinn", someone who wishes to help others and those she cares about acting less heroic, capable of doing questionable acts. Still, she is not evil, thus becoming an anti-hero.

Harley Quinn is of Jewish descent. Her favorite book is Clive Cussler's Sahara. The Joker claimed that she has HPV. Harley is a big fan of the Jurassic Park movies and the Shrek movies. Harley played baseball when she was a kid. Harley's favorite band is Guns N Roses. According to her, Ivy makes the funniest and smelliest farts. Harley Quinn is Bisexual.*