Kate Barker (born Arizona Donnie Clark; October 8, 1873 – January 16, 1935), better known as Ma Barker (and sometimes known as Arizona Barker and Arrie Barker), was the mother of several American criminals who ran the Barker–Karpis Gang during the "public enemy era" when the exploits of gangs of criminals in the Midwestern United States gripped the American people and press. She traveled with her sons during their criminal careers.

Barker gained a reputation as a ruthless crime matriarch who controlled and organized her sons' crimes. J. Edgar Hoover described her as "the most vicious, dangerous, and resourceful criminal brain of the last decade". She has been presented as a monstrous mother in films, songs, and literature. Those who knew her insisted that she had no criminal role and that Hoover created the allegations to justify her shooting by the FBI in 1935. Reports as of 2022 are consistent that Kate Barker's role in her sons' crimes was falsely created by the media to increase newspaper and media sales.