A group of 13 Nobodies who retained human form and are fighting to get their hearts back. They are from the popular Kingdom Hearts series. However, they are also the only villans who have a larger fan following than the main characters. Many members (such as Axel and Roxas) are paired together in yaoi relationships, canon or not. Mostly not. They were taken down member by member by Sora, the main character (who wield a giant KEY), and his many Disney and Final Fantasy friends. It is also interesting to note that Organization XIII only has one female member (Larxene) because Xion was not a true member and the rest are male.
Axel, Roxas, Demyx, and Xigbar are all Nobodies who are members of Organization XIII.