Hiruzen Sarutobi

The surname is Sarutobi. His given name is unknown. His surname, inspired by Sarutobi Sasuke, means "jumping like a monkey", further supported by his Summoning Technique which summons an ape. The First and Second Hokages also called him "Monkey". Masashi Kishimoto originally planned for the Third Hokage to be a dog, but eventually dumped the idea for being "too weird".

Many aspects of his character are borrowed from the Chinese literature classic Journey to the West; the monkey he summons bears a very strong resemblance to Sun Wukong, the protagonist of Journey to the West, and Sarutobi's chosen weapon is identical to Monkey's magical staff.

Background
The Third Hokage was a student of the First Hokage and Second Hokage, where he was teamed with Homura Mitokado and Koharu Utatane. Later in his life he became the sensei of Jiraiya, Orochimaru, and Tsunade, who would go on to become known as the "Legendary Three Ninja". The Third was the father of Asuma Sarutobi and the grandfather of Konohamaru. His favorite foods were dried black seaweed and sardines, with his least favorite being pickled vegetables. His favorite phrase was "the ultimate truth". He looked on Orochimaru as something like a son to him, seeing this in his death.

Soon after becoming his master, the Third came to appreciate Orochimaru's natural talent, even going so far as to tell Jiraiya to be more like Orochimaru. He also came to recognize an inner malice and a lust for power within Orochimaru, and tried to steer his student away from these personality traits. After taking the position of Hokage and occupying it for many years, the Third began to look for a successor to the title. While he hoped to be able to give the position to Orochimaru, it became apparent to the Third that Orochimaru was only interested in the role of Hokage as a way to get power. As such, the Third passed on the role of Hokage to one of Jiraiya's former students, Minato Namikaze.

After relinquishing his title, the Third began investigating a number of disappearances within Konoha. Upon reaching the source of the abductions, the Third found Orochimaru to be the one responsible. Learning that Orochimaru had kidnapped so many people so that he could experiment on them in the hopes of gaining immortality, the Third prepared to kill Orochimaru. Although Orochimaru gave him the opportunity, the Third hesitated due to his unwillingness to harm his favorite student, thus allowing Orochimaru to escape. Sometime after Orochimaru had left the village, the Fourth Hokage sacrificed his life to seal the Nine-Tailed Demon Fox within Uzumaki Naruto, forcing the Third to reassume the title of Hokage.

The Third was called The Professor due to his vast knowledge of jutsu, knowing numerous types of elemental attacks and purportedly all the jutsu within Konoha. The Third also seems to have had some sense of lecherousness in him, volunteering to help Jiraiya test his Transparent Escape Technique (invented for the purposes of voyeurism). He also fell victim to Naruto's Sexy Technique on more than one occasion, and even enjoyed talking with young girls in his spare time.

Part I
At the start of the series, the Third is one of the few people to not view Naruto Uzumaki as an embodiment of the demon fox, instead seeing him as a person. As such, Naruto came to be very fond of the Third, despite being fairly disrespectful to him. As the series progresses, the Third is frequently the source of information and wisdom, and passes his knowledge down to those younger than him.

Invasion of Konoha arc
When the invasion of Konoha begins, the Third is forced to do battle with Orochimaru, who infiltrated the village and planned Konoha's destruction just so that he could kill the Third. Soon after the battle begins, Orochimaru resurrects the first two Hokages so that the Third can feel the enjoyment of fighting a former master. In his old age, the Third is unable to be much of a match for the two Hokage, and is further inhibited by his desire to not hurt either. Although he uses his summon, Enma, to help him in battle, the Third is unable to make a dent in the two Hokage, and any damage that is done is simply regenerated.

Having no other choice, the Third uses a combination of shadow clones and the Dead Demon Consuming Seal to seal away the souls of his former masters. As he bids a heartfelt goodbye to the teachers he is sentencing to an eternal battle, he turns his attention to Orochimaru. Charging at Orochimaru and throwing aside his former pupil's Kusanagi, the Third attempts to seal Orochimaru's soul as well. Sensing what the Third is trying to do, Orochimaru calls his Kusanagi to him, stabbing the Third in the back.

Despite the fatal injury, the Third continues to try to remove Orochimaru's soul, unconcerned with the sword in his back due to death being guaranteed as a result of using the Dead Demon Consuming Seal. After an hour passes, the Third comes to terms with the fact that he is too old and weak to completely remove Orochimaru's soul. Doing what little he can, the Third seals Orochimaru's arms in the hopes that it will make up for allowing Orochimaru to escape years earlier, ensuring that Orochimaru will never again be able to use jutsu. As Orochimaru begins to curse his former master for what he has done, the Third bids Orochimaru farewell and hopes that they will meet again. Remembering a time when Orochimaru was happy, the Third dies, leaving Orochimaru alive, yet defeated. In the anime, as the Third dies, he sees Orochimaru not as the villain he has become, but as the pupil Sarutobi loved like a son.

During his battle with Orochimaru, the Third's likeness on the Hokage Monument cracked across the face. While the crack is fairly prominent due to its size, it doesn't always show up in the anime due either to a bad angle or a mistake by the animators. Later filler arcs try to address this discrepancy by filling up the crack, but the filling is revealed to be numerous exploding tags, and as such is removed.