Kenpachi Zaraki (更木 剣八, Zaraki Kenpachi) is the Captain of the 11th Division in the Gotei 13. His Lieutenant is Yachiru Kusajishi.

Kenpachi is a muscular Shinigami with a wild and aggressive appearance that fits his personality. He wears a sleeveless captain's haori which has a ragged look to it (assumed due to violence that accompanies the position of captain of the 11th Division). He styles his spiked-hair with small bells at its tips and wears a special eyepatch on his right eye created by the Shinigami Research and Development Institute to suppress his vast amount of spiritual energy. When he makes his first appearance the eyepatch is more elegant having a gold-like lining and having a chain as one of the straps, this changed after his defeat by Ichigo and has since worn a normal black eyepatch with normal straps. He has pronounced hairless eyebrow ridges and a huge scar running down the left side of his face, which he apparently gained long before he served in the Gotei 13, even before finding his future lieutenant, Yachiru Kusajishi. He is also one of the tallest Shinigami, towering at 202 centimeters (approximately 6 feet 6 inches), making him slightly taller than Yasutora Sado and almost double the height of his lieutenant. His stature is often exaggerated even more for dramatic purposes, especially in contrast with Yachiru's.

Kenpachi's unique hairstyle is partly due to the result of his habit to take a bath everyday before going to sleep, which is a necessity to him due to his strong perspiration. During these baths, he usually washes his hair with soap, making it stiff. He enjoys doing so because it's easy for him to set his hair to his preferred style. He once tried a hair treatment recommended by 1st Division Lieutenant Chōjirō Sasakibe, but his hair became too silky and was impossible to set for a while. Since then, Kenpachi has greatly disliked the lieutenant.

Kenpachi is once shown attaching the bells to his hair, which apparently takes a while to accomplish. The highest bell in particular takes him several hours to attach, as the tip of his hair is just beyond his reach. Occasionally, 11th Division 5th Seat Yumichika Ayasegawa offers to do it for him, only to be turned down by Kenpachi due to thinking that it's weird for someone else to style his hair.

Although he's known to be a violent fighter, Kenpachi's actions tend to be for the best and is usually portrayed comically (this comical shift is primarily centered on his appearances in the anime and omake, with the exception his casual conversations with his lieutenant). He is usually depicted as a person who has a very poor sense of direction, asking Yachiru for directions (who then randomly points in a direction, as her sense of direction is just as bad). Kenpachi lives for battle and enjoys a good fight more than anything. He even holds back in an effort to make any fight last longer. He also claims that injury and death are nothing but the price one pays for a good fight. Despite his division being the most blood-thirsty squad of the Gotei 13, the 11th Division have their own code of ethics, which is different from the rules and regulation of Soul Society.

Although he thrives for battle, Kenpachi has shown to have emotions and cares for Yachiru. Kenpachi and Yachiru have been close, ever since they met, and have a father-daughter-like relationship (making Yachiru one of the few people he cares for, along with 11th Division 3rd Seat Ikkaku Madarame and 11th Division 5th Seat Yumichika Ayasegawa).

Aside from Yachiru, Kenpachi deeply gives meaning to his name. Following his fight with Ichigo Kurosaki, Kenpachi talks about the pain of not having a name, as he lived his early years without one. This causes him to feel guilty that his sword isn't acknowledged by its own name. Since then, he has strived to learn its identity.

Despite his tendency to be brutal, Kenpachi usually stops a fight if his opponent is too injured to fight back, claiming that he isn't interested in fighting "weaklings who can't fight anymore; nor is he obligated to deal a death blow to anyone who isn't capable of fighting any longer". However, he will unhesitatingly kill his opponent if they refuse to end their fight, as seen during his battles with Kaname Tōsen and Nnoitra Jiruga.

On multiple occasions, Kenpachi has shown to greatly respect those who can defeat him in a fight and to those who can push him to his limit. Ever since Ichigo handed him his first known loss(though Ichigo also considers their fight a loss for him), Kenpachi has considered the latter a member of his division. He also expresses his willingness to engage him in a rematch every time they meet, only to be turned down as Ichigo already considers themselves as friends. Nevertheless, Kenpachi still challenges him in a duel, as evidenced when he aided Ichigo in his fight against the Bount (where he gave "his blessing," stating that in doing so would make Ichigo stronger for "their anticipated fight").

Kenpachi also strongly believes that fun comes before working. In every battle, he tries to get as much enjoyment out of it as possible. One example is when Kenpachi sends his 5th seated officer, Yumichika, to fend off the Bount in Karakura Town, as he is the only high-ranking officer who wasn't busy, or rather, busy having fun, as Yachiru was snacking and Ikkaku was napping. During his free time, Kenpachi always takes his afternoon nap. He doesn't have a particularly favorite dish, but he particularly hates nattō.

It seems that Kenpachi sometimes contradicts his own logic in fighting. On the one hand, Kenpachi wishes to increase his own personal power. On the other hand, he conceals his strength to enjoy a fight for as long as possible. Irrational to a certain extent, Kenpachi is one of the most complex characters in the series, as he exhibits a wide range of traits: lethargic, bloodthirsty, rebellious, empathetic, and wise.