Supergirl is a character produced by DC Comics. She is depicted as a female counterpart to the DC Comics iconic superhero Superman. There are three Supergirls that made a one-time appearance and five to take up the mantle.
Many Superman stories feature one time appearances of a female version of Superman as a story gimmick.
Queen Lucy, Super Girl
In Superboy #5 (November-December 1949) in a story titled 'Superboy Meets Supergirl' Superboy met Queen Lucy of the fictional Latin American nation of Borgonia. She was a stellar but not superhuman athlete and scholar. Tired of her duties and wanting to enjoy a normal life Queen Lucy traveled to Smallville where she met Superboy and soon won his heart. Superboy put on a show with her where he used his powers to make her seem superhuman, during this contest she was called Super-Girl wore a tan dress with a brown cape and Superboy's 'S' symbol. Superboy later saved her from a scheming minister and she returned to the throne leaving Superboy to wonder if she ever thought of him.
In the Superboy #78 story titled "Claire Kent, Alias Super-Sister", Superboy saves the life of an alien woman named Shar-La from crashing. After he ridicules her driving for being a girl, Shar-La turns Superboy into a girl. In Smallville, Clark claims to be Claire Kent, an out-of-town relative who is staying with the Kents. When in costume, he appears as Superboy's sister, Super-Sister, and claims the two have exchanged places. As a girl, he is ridiculed and scorned by men, and wants to prove he's as good as he always was. In the end, it is revealed that the situation is an illusion created by Shar-La, and Superboy learns not to ridicule women.
In Superman #123 (August 1958), Jimmy Olsen uses a magic totem to wish a "Super-Girl" into existence as a companion and aid to Superman; however, the two frequently get in each other's way until she is fatally injured protecting Superman from a Kryptonite meteor. At her insistence, Jimmy wishes the dying girl out of existence. DC used this story to gauge public response to the concept of a completely new super-powered female counterpart to Superman. In the original issue in which this Super-Girl story was printed, she had blond hair and her costume was blue and red like Superman's. Early reprints of this story showed her with red hair and an orange and green costume, to prevent readers from confusing her with the then current Supergirl character. Much later, the story was again reprinted in its original form.
Kara Zor-El was the last survivor of Argo City of the planet Krypton, which had survived the explosion of the planet and had drifted through space. When the inhabitants of the colony are slain by Kryptonite, Kara is sent to Earth by her father Zor-El to be raised by her cousin Kal-El, known as Superman. Fearing that she might not be recognized by Superman, Kara's parents provide a costume based on the Man of Steel's own.
On Earth, Kara acquires super-powers identical to Superman's and adopts the secret identity of Linda Lee, an orphan at Midvale Orphanage. She conceals her blonde hair beneath a brunette wig and functions as Supergirl only in secret, at Superman's request, until she can gain (in his opinion) sufficient control of her powers. After being adopted by Fred and Edna Danvers, Superman decides his cousin is ready to begin operating openly as Supergirl.
Issue #8 of the Superman/Batman series originally published in 2004 re-introduced Kara Zor-El into DC continuity. Like the pre-Crisis version, this Kara claims to be the daughter of Superman's uncle Zor-El and aunt Alura In-Ze. Unlike the traditional Supergirl origin, Kara was born before Superman; she was a teenager when he was a baby. She had been sent in a rocket in suspended animation to look after the infant Kal-El; however, her rocket was caught in the explosion of Krypton, became encased in a kryptonite asteroid, and she arrived on Earth years after Kal-El had grown up and became known as Superman. Due to this extended period of suspended animation she is "younger" than her cousin, relatively speaking (she is referenced to be about 16, while Superman is portrayed to be about 35+). At the end of "The Supergirl from Krypton" arc, her cousin Superman officially introduces her to all the heroes of the DC Comics Universe, then she adopts the Supergirl costume, and accepts the name.
After the post-Crisis reboot of Superman continuity in the late 1980s, Supergirl's origin was completely rewritten. No longer was she Superman's cousin, or even Kryptonian. In Superman v2, #16 (April 1988), a new Supergirl debuted as a man-made life-form (made of synthetic protoplasm) created by a heroic Lex Luthor of a "pocket universe". Lex implanted her with Lana Lang's memories, and she could shapeshift to resemble Lana Lang. Matrix even believed herself to be Lana for a time. She wore a miniskirted version of Superman's costume, but Matrix did not have Superman's exact powers. While she possessed flight and super-strength (like Superman), she could also employ telekinesis, shape-shifting and a cloaking/invisibility power (her cloaking power made her undetectable even to Superman himself).
Matrix's Supergirl form resembled the pre-Crisis Supergirl. She lived in Smallville with the Kents, who treated "Mae" like their own daughter. While new to Earth, Matrix began a romance with the DC Universe's Lex Luthor until she realized Luthor's evil nature. She left him to find her own way in the world, serving for a time as a member of the Teen Titans and a hero in her own right.
Beginning in September 1996, DC published a Supergirl title written by Peter David. The 1996 Supergirl comic revamps the previous Matrix Supergirl by merging her with a human being, resulting in a new Supergirl. Many old elements of the pre-Crisis Supergirl are reintroduced in new forms. The woman that Matrix merges with has the same name as pre-Crisis Supergirl's secret identity, Linda Danvers. The series is set in the town of Leesburg, named after pre-adoption secret identity, Linda Lee. Linda's father is named Fred Danvers, the same as pre-Crisis Supergirl's adopted father.
As the series begins, Matrix sacrifices herself to save a dying woman named Linda Danvers, and their bodies, minds, and souls merge to become an "Earth-Born Angel", a being that is created when one being selflessly sacrifices him or herself to save another who is, in every way, beyond saving. As the angel, Supergirl loses some of her powers but gains others, including fiery angel wings and a "shunt" ability that allows her to teleport to any place she has been before.
A Supergirl named Cir-El appears in 2003's Superman: The 10 Cent Adventure #1, claiming to be the future daughter of Superman and Lois Lane. Although she has super-strength, speed, and hearing like Superman, she can only leap great distances. She also possesses the ability to fire blasts of red solar energy. Her alter ego is a street person named Mia. She is later found to be a human girl who was altered by Brainiac on a genetic level to appear Kryptonian; she dies thwarting a plot involving Brainiac 13. Superman Vol. 2 #200 implies that when the timeline realigned itself, Cir-El was no longer in continuity. Cir-El is unique among the various incarnations of Supergirl; she is the only one who is not a blonde.
Several different versions of Supergirl have appeared in continuity.
An alternate version of Kara Zor-El from the parallel world, Earth-Two, the cousin of Superman (Kal-L).
Laurel Gand was the post-Crisis/Glorithverse replacement for the pre-Crisis Supergirl in the Legion of Super-Heroes, after the latter was removed from continuity following The Man of Steel reboot of Superman. Originally, Laurel was simply known by her given name. A younger version of Laurel took the superhero code name "Andromeda" shortly before the Zero Hour reboot of the Legion; post-reboot, Laurel remained Andromeda.
Supergirl of the 853rd century, later revealed to be the daughter of post-Crisis Linda Danvers and Silver Age style Superman from the Many Happy Returns story arc.