Missing-nin

are ninja who left their village without the intention of returning and severing ties with the said village, often because they have committed criminal acts or to pursue other personal gains. The ninja village that they are from will often try to track them down and eliminate them. Several missing-nin (such as Zabuza Momochi) do not stop wearing their forehead protector, while others (such as Orochimaru) may discard them. Akatsuki members who do retain their headbands carve long, horizontal scratches across the symbol, to show they have rescinded their allegiances and rejected their villages. Kirigakure has a special hunter-nin task-force whose only objective is killing traitorous ninja. Not only is this done as a punishment for treason, but also to protect the secrets of the village, since it is possible to learn some of the village's techniques from the autopsy of their users. The ninja organisation Akatsuki is composed mostly of S-class missing-nin, except for Nagato and Konan, who are the leaders of Amegakure. Most of the missing-nin throughout the series are antagonists.

Depending on the village leader's decisions, the missing-nin in question may be given leniency. The most prominent example is Sasuke Uchiha, who is not marked for death by the Fifth Hokage, Tsunade, as a favour to Naruto Uzumaki, and is instead to be brought back as a Konohagakure citizen. However, according to Kakashi Hatake, a missing-nin is typically marked for death simply for defecting, and such mercy is rare.

Later, when Sasuke infiltrated Kumogakure and attempted to abduct their Jinchūriki, Killer B, then attacked the Kage Summit, the Five Kage elevated his status to an international criminal, meaning that he is a missing-nin now wanted on a global-scale.

The Bingo Book contains information on every missing-nin and is given to every Jōnin and ANBU member by their respective Kage.