A Zanpakutō (斬魄刀; literally, Soul-Cutter Sword) is the main weapon of the Shinigami, the Arrancar, and the Visored. The Shinigami art of wielding a Zanpakutō is called Zanjutsu (斬術; literally, swordsmanship).
The Zanpakutō of low-ranking Shinigami are called Asauchi and do not have names, but the Zanpakutō of Shinigami of rank have names. In its sealed state, a Zanpakutō has the form of a Japanese sword. Such weapons are unique swords generated from their owner's souls. Its shape differs depending on its owner.
Zanpakutō are the trademark weapons of the Shinigami. Capable of cutting spiritual bodies, they are among the few weapons which can be used to combat Hollows. Each Shinigami carries a Zanpakutō, and each Zanpakutō is unique: the swords are reflections of a Shinigami's power and soul, and sentient beings unto themselves. The Zanpakutō's name is the name of the living spirit which empowers the sword and lends its strength to the Shinigami who wields it. These beings can vary greatly in appearance, and have their own distinct personalities, which match their owner's.
A Zanpakutō's shape and abilities are based on their Shinigami's soul. Once a Shinigami learns his/her sword's name, they can communicate with one another and grow stronger together. Zanpakutō are born with their Shinigami, and they die along with their Shinigami. Shinigami use them in battle as a reflection of their heart. When released, they can display a vibrant power. They are one with the Shinigami, and they share a Shinigami's conviction.
Inside each Zanpakutō is an incarnation which manifests itself upon the Zanpakutō's transformation. The first step is to acquaint oneself with this incarnation.
An Arrancar's primary weapon is the same as a Shinigami's, but unlike a Shinigami's Zanpakutō, the blade is an embodiment of the Hollow's power.
- All Asauchi are forged solely by Ōetsu Nimaiya. Since the birth of Soul Society itself there has never been a Shinigami who awakened to his or her own Zanpakutō without wielding an Asauchi that he forged.
- Because they are part of their owner's soul, a Zanpakutō cannot be replaced, though it will slowly regenerate if it is broken.
- The only thing that can heal a broken Zanpakutō is its own wielder's force of will, reiatsu, and the time required to infuse the Zanpakutō with that reiatsu. This only relates to one's Shikai. The destruction of a Shikai and the destruction of a Bankai hold quite different meanings. A destroyed Bankai can never be restored to its original form.
- The size of the Zanpakutō reflects the amount of the swordsman's spiritual power. Exceptions to this rule are beings of immense power, who are required to actively control the size of their Zanpakutō.
- If a Shinigami pierces the chest of a Human with their Zanpakutō and channels their Reiryoku through it into the Human's body, it will transform this Human into a Shinigami temporarily. This process does not have a high chance of viability even when the Human in question has a high level of spiritual energy, and if the method does fail, the Human will die.
- Every Zanpakutō has its own name, which the wielder must learn.
- A Zanpakutō can determine if its wielder is worthy of its power.
- Zanpakutō have a true form. This true form resides inside their Shinigami. A Zanpakutō has a mind and a body, which control their powers. Shinigami can grow more powerful by communicating with them.
- Zanpakutō possess their own Reiatsu, which can be sensed as any Reiatsu can and is identical to their wielder's, though with subtle differences.
- No matter what form (or size) a Zanpakutō takes, it is always virtually effortless for its owner to wield because it is a part of its owner's soul. Shinigami captains all consciously keep their Zanpakutō in a manageable size, or else they would be holding Zanpakutō the size of skyscrapers, so one cannot judge one's opponent's strength solely by the size of their Zanpakutō.
No Zanpakutō in existence has a Shikai and a Bankai which use unrelated abilities.