Sannin

The were three renowned ninja from Konohagakure, hailed as the greatest of their time.

History
As genin, the three were teamed together under the leadership of Hiruzen Sarutobi, the Third Hokage. For one of their earlier training exercises, Hiruzen gave them a bell test: Jiraiya failed to get a bell - he repeatedly fell for Hiruzen's traps - and was tied to a stump as punishment. During their time as Hiruzen's students, they all learned to use the Summoning Technique, which they perform with their left hands. Despite being a team and having accomplished great things together, the three members were always in constant disagreement with one another, which Tsunade referred to as a "three-way deadlock". Once they became skilled ninja able to look after themselves, Hiruzen's team disbanded.

Despite the official dissolution of their team, the three continued to work together during the Second Shinobi World War. During one battle with Amegakure's Hanzō, they were the only Konoha ninja to survive Hanzō's attacks. As a reward for this, Hanzō dubbed them "Konoha's Legendary Sannin". However, that same battle was the last one the three fought together: Jiraiya afterwards decided to remain in Ame, to repent for his part in the war; the horrors of the war badly affected Tsunade as well, prompting her to abandon the life of a ninja; Tsunade had left Konoha by the time of Jiraiya's return to Konoha, and Orochimaru would eventually leave the village as well, a consequence of his criminal activities; Jiraiya tried and failed to convince Orochimaru to return, and subsequently dedicated himself to monitoring Orochimaru's activities, a task that took him away from Konoha for long periods of time.

Because of their skills, each of the Sannin have been considered for the position of Hokage at one time or another:
 * When Hiruzen decided to retire, Orochimaru applied to replace him as Fourth Hokage. He was declined for the position, as Hiruzen felt that Orochimaru lacked understanding of what it means to be a ninja of Konoha.
 * Following the death of the Fourth Hokage, Hiruzen wished for Jiraiya to become the Fifth, but Hiruzen was unable to locate him.
 * Following Hiruzen's death, the Konoha Council selected Jiraiya to be the Fifth Hokage, but he declined out of lack of interest. He proposed Tsunade for the position instead, which she is ultimately convinced to accept.
 * When Tsunade was rendered comatose following Pain's Assault, the Land of Fire's daimyō remarks that he would have liked Jiraiya to replace her as the Sixth, but Jiraiya was already dead.

Despite the rivalry that existed between Orochimaru and Jiraiya, the constant arguing between Jiraiya and Tsunade, and Orochimaru's defection from Konoha placing him at odds with both Jiraiya and Tsunade, the three nevertheless remained attached to each other: when rumours of Orochimaru's death reached Konoha, Jiraiya and Tsunade discussed it together with disbelief and sadness; Tsunade anticipated she would have a similar reaction were anything to happen to Jiraiya, and did indeed cry following his death. When Tsunade learned that Orochimaru was still alive, she blamed him for Jiraiya's death, believing Jiraiya would still be alive had Orochimaru not betrayed Konoha. Orochimaru, though he noted remorse for Jiraiya, argued it was better that things happened as they did, otherwise Jiraiya may not have remained the quality-shinobi that he was.

Renown

 * Tsunade - granddaughter of the First Hokage; addicted to gambling but chronically unlucky; revolutionised the medical-ninja system and the entire system of rules that medical ninja abide by; trained Shizune and Sakura Haruno, among others, in the art of medical ninjutsu; eventually became Fifth Hokage. Can summon slugs.
 * Orochimaru - called the prodigy of his generation; endeavoured to gain immortality via means of kinjutsu in order to learn every technique in existence; defected from Konoha, joined Akatsuki, and founded Otogakure; taught Anko Mitarashi (and the other members of Team Orochimaru), Kabuto Yakushi, and Sasuke Uchiha. Can summon snakes.
 * Jiraiya - wandered the world and trained at Mount Myōboku; author of The Tale of the Utterly Gutsy Shinobi and the Icha Icha series of novels; became the teacher of the Ame Orphans, Minato Namikaze (and the other members of Team Jiraiya), and Naruto Uzumaki; died while investigating Pain, but not before gaining intel that contributed to Pain's ultimate defeat. Could summon toads.

Trivia

 * The Sannin are named after the characters in the Japanese folktale Jiraiya Goketsu Monogatari, however, only Jiraiya's kanji in his name are different than his source inspiration.
 * One of the earliest Japanese sansukumi-ken was "Slug, Snake, Frog", more commonly known as rock, paper, scissors. In this variation, the Frog is afraid of the Snake, the Snake is afraid of the Slug, and the Slug is afraid of the Frog. This is influenced by the Sansukumi way of thinking, where it keeps the three objects in a deadlock.
 * Each of the Sannin has trained one member of Team Kakashi: Jiraiya trained Naruto, Tsunade trained Sakura, and Orochimaru trained Sasuke.
 * Team Konohamaru has a direct relationship with Team Hiruzen. In the case of Sarada and Boruto, one or both of their parents were trained by a Sannin. In the case of Mitsuki, his parent was a Sannin. Their team leader, Konohamaru, is Hiruzen's grandson.
 * Several years prior to the events of Naruto Shippūden the Movie: The Will of Fire, Hiruzen assigned the Sannin to assassinate Hiruko for conducting illegal experiments. This failed, as Hiruko escaped with his research by the time the Sannin reached his lab.