The Golden Age Batgirl, Betty Kane was introduced into publication in 1961 by Bill Finger and Sheldon Moldoff, first appearing in Batman #139.
She was replaced by Barbara Gordon in 1967, who later came to be identified as the iconic Batgirl. The lass debuted in Detective Comics #359 (1967) by writer Gardner Fox and artist Carmine Infantino, introduced as the daughter of Gotham City police commissioner James Gordon.
Later, in the Alan Moore's graphic novel Batman: The Killing Joke where, in her civilian identity, she is shot by the Joker and left paraplegic. She is recreated as the computer expert and information broker Oracle by editor Kim Yale and writer John Ostrander.
Batgirl has officially been represented by four different characters - and two claimants - beginning with her introduction in 1961.
During the Golden Age, a female character was introduced as a love interest for Robin. Betty Kane as "Bat-Girl" was depicted as the niece of and Robin-like sidekick to the original Batwoman. In 1964, however, editor Julius Schwartz asserted that Bat-Girl and other characters in the Bat-Family should be removed considering the decline in sales and restored the Batman mythology to its original conception of heroic vigilantism. During the Crisis on Infinite Earths storyline, Betty Kane was retconned out of existence.
Mary Elizabeth "Bette" Kane is a reinvented version of the Betty Kane character during the Golden Age. As her original characterization was retconned out of existence during the Crisis on Infinite Earths storyline, a discrepancy arose where her Bat-Girl character had joined the west coast version of the Teen Titans but simply disappeared. The character was reintroduced as Bette Kane and the alias of Flamebird. Following Infinite Crisis, the character's past as Bat-Girl was hinted at as being a part of continuity. However, that reference included a revamped origin of the character and it may or may not have been the current Bette Kane.
During the run of the Batman television series, DC editorial was approached about adding a female character back into the Batman family. Revising the character history and motivation, Julius Schwartz created Barbara Gordon. This character held the role of Batgirl from 1967 to 1988 when she was retired by DC editorial decision. The character's role was changed to a paraplegic source of information for all members of the Batman family and codenamed Oracle. She was later restored as Batgirl during The New 52 relaunch of the entire DC publication line in 2011.
During the No Man's Land storyline, Cassandra Cain was given the role of Batgirl under the guidance of Batman and Oracle. Written as the daughter of assassins David Cain and Lady Shiva, she is trained from early childhood to read human body language instead of developing verbal and written communication skills as part of her father's conditioning to mold her into the world's deadliest assassin. However, after committing her first murder, she vows to never again use her martial-arts prowess to kill. In 2000, she became the first Batgirl to star in an eponymous monthly comic book series as well as one of the most prominent characters of Asian descent to appear in American comics. The series was canceled in 2006 and Cassandra Cain abandoned the role of Batgirl shortly thereafter. Years later, Cassandra rejoined the Batman family under the moniker Blackbat.
Stephanie Brown was formerly known as Spoiler and then as the first in-continuity female Robin until her apparent death in 2006. Following her return to comics in 2009, she assumed the role of Batgirl. She maintained this position until 2011, the relaunch of the DC imprint under The New 52. The character reappeared in the DCU in Batman #28, as Spoiler.
Also known as the Huntress. For a brief time during 1999's No Man's Land storyline, Helena Bertinelli assumed the mantle of Batgirl. After violating Batman's code against extreme violence, she was stripped of the mantle and returned to her alias of Huntress.
Charlotte "Charlie" Gage-Radcliffe
After Cassandra Cain abandoned the role a mystery character appeared as the new Batgirl in the Birds of Prey comic. Possessing superpowers, the teen claimed the empty mantle in an attempt to honor the character. However, Barbara Gordon quickly dissuaded the teen from continuing in the role. Charlie Gage-Radcliffe acquiesced, but modified her costume and changed her name to Misfit.