It is the duty of the Gotei 13 to protect Soul Society and the Human World from Hollows and other threats of a similar nature. Doing so takes great leadership and only the strongest of Shinigami are up to the task. Even still, many have fallen in the line of duty.
Current: Shunsui Kyoraku
Former captain of the 8th Division, Shunsui Kyoraku took the mantle of Captain-Commander in place of Captain-Commander Yamamoto. As Captain-Commander, Shunsui leads not only the 1st division but the entire Gotei 13. His Zanpakuto has the ability to make children’s games real, with lethal consequences for rule breakers.
Former: Shigekuni Yamamoto-Genryusai
Genryusai Shigekuni Yamamoto was the oldest member of the Gotei 13 and led them as Captain-Commander for 1000 years. He is a master strategist who is nearly unmatched in hand-to-hand combat as well as swordplay.
Current: Soi Fon
Soi Fon leads the 2nd Division as its captain. She is also a master at assassination. Her Zanpakuto can kill an enemy in only two strikes, and also doubles as an artillery cannon. Furthermore, she is a master at hand-to-hand combat and Kido as well as a combination of the two, called Shunko.
Former: Yoruichi Shihouin
Yoruichi Shihoin was the previous 2nd Division captain and Soi Fon’s mentor. She has a playful personality and rarely takes anything seriously outside of battle. Her hand-to-hand combat abilities are practically unrivaled.
Former: Roujuuro Otoribashi and Gin Ichimaru
Rojuuro Otoribashi, nicknamed "Rose", was the 3rd Division captain 100 years before the start of the series. He originally lost his position after being framed for a crime but regained his post over a century later when the true culprit was revealed. His Zanpakuto can create shockwaves through the manipulation of sound.
Gin Ichimaru is an unnerving character, constantly smiling for no apparent reason. His Zanpakuto has the ability to extend great distances at high speeds, allowing him to impale and/or cut any target almost instantly.
Anime-only: Shuusuke Amagai
Shuusuke Amagai filled Gin’s vacant spot after learning to utilize the Bankai of his Zanpakuto to control fire. Amagai is the only captain who is exclusive to the anime, appearing in a filler arc.
Former: Retsu Unohana
Retsu Unohana led the 4th division, which specializes in healing. Her Zanpakuto takes the form of a large manta ray-like creature which breathes a healing mist, and can also be used for transportation.
Current: Shinji Hirako
Shinji Hirako was one of the several Shinigami framed for crimes 100 years before the start of the series. After the culprit's arrest, he resumed his former position as captain. His Zanpakuto is called Inverted World and makes everything backwards for his opponent (up is down, left is right, etc.)
Former: Sousuke Aizen
Sousuke Aizen is a genius-level individual who is almost always calm and collected, rarely displaying anything other than a cool demeanor. Aizen is also a very devoted individual, going to any means in order to achieve his objectives.
Current: [Byakuya Kuchiki]8https://myanimelist.net/character/907/)
Byakuya Kuchiki leads the 6th Division as one of Soul Society’s deadliest fighters. A child prodigy and extremely serious person, Byakyua’s Zanpakuto can split into thousands of small blades that he controls at will to cut his opponents to ribbons.
Former: Ginrei Kuchiki
At some point in time Ginrei Kuchiki, Byakuya’s grandfather, led the 6th Division, although little is known of his career.
Current: Sajin Komamura
Sajin Komamura is the immensely powerful, canine-headed leader of the 7th Division. His Zanpakuto can create a giant suit of armor, with an equally giant sword, that follows his every move. Komamura is a very kind person, always willing to forgive others.
Former: Love Aikawa
Love Aikawa was one of the captains framed for crimes he did not commit. His Zanpakuto can turn into a giant, spiked club that ignites itself and shoots fire.
Former: Shunsui Kyoraku
The 8th Division is currently without a captain due to Shunsui Kyoraku’s promotion (see above).
Former: Kensei Muguruma , Kaname Tousen
Kensei Muguruma was another individual who lost his post due to being framed, and later regained his position as captain. His Zanpakuto had the ability to create powerful air blades that would explode on impact.
Kaname Tousen was born blind and his abilities take advantage of this, manipulating the sense of sight to put his opponents at a disadvantage. His creed in life is to "take the path with the least bloodshed", but he is perfectly willing to shed that minimal amount of blood.
Current: Toushirou Hitsugaya
Toshiro Hitsugaya is the youngest of the captains and often gets stuck with duties that the other captains do not want to perform due to his youth. Controlling a dragon made of ice, he seeks to prove himself to his seniors.
Former: Isshin Kurosaki
Isshin Kurosaki led the 10th Division before becoming an exile in the Human World.
Current: Kenpachi Zaraki
Kenpachi Zaraki is the 11th holder of the Kenpachi title as well as captain of the 11th Division. Zaraki lives for battle, fighting like a berserker to inflict maximum damage to his opponents while holding little regard for his own safety. In terms of raw power, Zaraki is the strongest Shinigami.
Former: Retsu Unohana
Retsu Unohana led the 11th Division during her time as Kenpachi (see above).
Current: Mayuri Kurotsuchi
Mayuri Kurotsuchi, mad scientist, heads the 12th Division. Sadistic and cruel, there is little Kurotsuchi would not do in the name of science.
Former: Kisuke Urahara
Kisuke Urahara was exiled after being blamed for someone else's crimes 100 years ago. He then set up a shop in the Human World, which sells items imported from Soul Society.
Current: Juushiro Ukitake
Jushiro Ukitake is a sickly man, but a powerful one. His morals are strong and he will always use his abilities to protect those around him. His Zanpakuto can absorb energy attacks and fire them back at his enemies.
These Captains defend their home with their lives and the world of "Bleach" would be very different without them.