Batgirl is a heroic mantle worn by various women through the modern heroic age. In most cases, Batgirl has been supported and endorsed by Batman and is usually a trained member of the Bat Family; allies in Batman’s war on crime.
A 2nd-generation mantel, after the initial Bat-Girl, who chose to model her name and look after her mentor, Batwoman, the second Batgirl’s name was not chosen by the bearer but was used as a descriptor of the heroine by those she encountered as she dressed in similar garb to the Batman to resemble a bat. The fourth Batgirl's "true" name temporarily became the name of the mantle by the Bat Family due to their lack of knowledge of her civilian name; using her codename to refer and address her until the revelation of her given name.
Bat-Girl (Betty Kane)
The first woman to posses the name was Betty Kane. Known as the Bat-Girl, Betty was the niece of Katherine "Kathy" Kane, the first Batwoman.
Joining her aunt in costumed heroics alongside Batman and Robin, Betty chose to done the costume after becoming infatuated with Robin; laying aside her olympic career chasing after him in spite of his disinterest in her.
Continuing after her aunt's retirement and death at the hands of the League of Assassins, Betty created a new mantle for herself as "Flamebird" and continued to pursue Robin, now named "Nightwing", as a member of the Teen Titans.
Batgirl (Barbara Gordon)
The second bearer of the name, and the creator of the current mantle line, was Barbara Gordon; who conjured the guise as a fancy dress costume to surprise her uncle, James Gordon. However, circumstance saw that she prevented a heist by the Killer Moth while in the costume and became known as “the Batgirl” due to the way she was dressed like Batman.
Having tasted superheroics and having previously attempted to assist heroes such as the Justice Society in an attempt to find meaning in her life, Barbara continued wearing the “Batgirl” costume while pursuing acts of heroic vigilantism in Gotham City. While initially giving her the opportunity to abandon this pursuit, Batman eventually brought her under his tutorship to make her more effective; his ward, Robin, quickly becoming infatuated with her.
After an established career, Barbara Gordon eventually retired the mantle and returned to civilian life.
Batgirl (Helena Bertinelli)
When Gotham City was cut off from federal aid for a year after a devastating earthquake, Helena Bertinelli, formally possessor of the Huntress mantle, fashioned herself as a new Batgirl to emerge in the wake of Batman’s absence and established a territory devoted to the protection of civilians as the city began to divide into various tribal groups.
Come Batman’s return to the city, the Helena began operating under his instruction, however, due to her fierce independent streak and Batman’s own high expectations of his associates, the mantle of Batgirl was eventually stripped from her to be passed on to another.
Batgirl (Cassandra Cain)
The daughter of David Cain, one of Bruce Wayne’s original mentors, Cassandra Cain was initially an unnamed seventeen-year-old who boarded with Barbara Gordon during Gotham City’s tenor as a No Man’s Land, acting as one of Gordon’s field agents in her capacity as Oracle.
Following her intervening on an assassination attempt by her father, Cassandra was given the mantle of Batgirl following Helena Bertinelli’s removal from the role.
Supported by both Barbara Gordon and the Batman, Cassandra operated as Batman’s field agent on numerous occasions, demonstrating herself as a loyal and capable associate. Following a debacle where she was abducted by her father and Deathstroke and drugged into being a killer, Batman finally decided to bring her fully into his family; officially adopting her as his daughter.
Following a secretive career as a much darker Batgirl than the original, Cain passed on the mantle to her friend, Stephanie Brown, in the wake of Bruce Wayne’s suspected death.
Batgirl (Stephanie Brown)
Initially known as the Spoiler, Stephanie Brown began her career in heroics as an act of rebellion against her criminal father; deliberately listening in on his heists and then dressing in costume to inform Batman and Robin, “spoiling” her father’s schemes.
Following her father’s death, Stephanie continued operating as the Spoiler to continue socializing with Robin in spite of both Batman and Robin’s insistence that she retire.
After a brief tenor as Robin and a disastrous attempt to prove her worth to Batman, Stephanie spent a year in Africa before returning to Gotham to operate once again as the Spoiler.
In the wake of Batman’s suspected death, Stephanie was given the mantle of Batgirl by Cassandra Cain and received new training and support from Barbara Gordon.
While Barbara Gordon is considered to be the first Batgirl in some comic canons, Betty Kane was actually the first character to posses the role; appearing as Bat-Girl during the DC Golden Age before the first crisis.