Martha was born in Gotham City to the wealthy Kane family. Unlike her family she decided to not join the family business of running Kane Chemicals and instead focused on charity work. In her youth she fell in love and married Thomas Wayne and eventually had a son, Bruce Wayne. One night while walking home from the movie theater with Thomas and Bruce the family is confronted with a gun by Joe Chill.
Similar to the original timeline Thomas, Martha and Bruce take a shortcut through an ally and are confronted by Joe Chill. However instead of Thomas and Martha being gunned down by Joe Chill, Bruce is shot instead. As Thomas Wayne is beating Chill to death, Martha descends into insanity cradling her sons body; She creates a "Joker smile" from her son's blood as her sorrow turns into insane laughter. The result being that while Thomas becomes the Batman of this universe, Martha becomes The Joker. Many years Batman later confronts and interrogates Yo-Yo for the Joker's whereabouts and the location of Judge Dent's twin children whom she kidnapped. Thomas also compares Eobard Thawne's deranged psychosis to the Joker's insanity.
After the timeline was restored, Martha and her husband Thomas were murdered in front of Bruce Wayne by Joe Chill in Crime Alley.
- Justice League: The Flashpoint Paradox (flashback)
- Justice League: War (mentioned)
- Batman vs. Robin (flashback)
- Batman: Bad Blood (flashback)
- Justice League Dark: Apokolips War (flashback)