Hashirama was originally the leader of the Senju clan. Under his leadership the Senju clan came to be regarded as one of the two most powerful clans in the world, rivalling the renowned battle-oriented Uchiha clan. Because of this, when someone hired the Senju clan, the opposing side would hire the Uchiha clan and vice-versa, causing frequent battles between the two. Eventually growing tired of the constant fighting, Hashirama and his clan approached the Uchiha and offered a truce with them. Allied with Madara and his clan, the two groups founded Konohagakure.
When deciding who should become the leader of Konoha, the villagers selected Hashirama over Madara for the title of First Hokage. Fearing that Hashirama would oppress the Uchiha, Madara left the village, and challenged Hashirama's rule. After an intense battle that included the Nine-Tailed Demon Fox, Kurama, Hashirama defeated Madara; and Hashirama's wife Mito became Kurama's first jinchūriki by sealing it within herself. In the aftermath of their battle, Madara was believed to have been killed, and the Valley of the End was created. To commemorate the battle, two statues, of Madara and Hashirama, were carved into the borders of the valley.
During his time as Hokage, Hashirama came into possession of a scroll filled with, among other skills, various kinjutsu, which he sealed away in order to keep the techniques within it a secret. He also defeated Kakuzu, who had been sent to assassinate him by Takigakure. At some point, Hashirama gained control of several tailed beasts. He spread these beasts to other, newly-formed villages in an attempt to maintain peace and equalise the powers between the nations, but it did not stop the outbreak of the First Shinobi World War. Thinking about the future of Konoha, he and his younger brother, Tobirama Senju, trained the young Hiruzen Sarutobi. Hashirama died shortly after the founding of Konoha in one of the many wars that were raging during this revolutionary era, but not before passing on the title of Hokage to Tobirama.
Hashirama was shown to be a very calm and collected person, as well as kind and caring, with a deep sense of loyalty, great charisma and negotiation skill. He saw the people of Konoha as a part of his own family, and his legacy took a firm root in the village. He was also shown to be a very wise and insightful man, as he passed on great teachings to Hiruzen. It was he who first believed that all Konoha shinobi should show true loyalty to each other, and that a Kage must be willing to put his life on the line for his village to set an example for all others. This belief of his is known as the "Will of Fire". Hashirama also seemed to have a sense of honour regarding his opponents and, despite their rivalry, possessed great respect for Madara Uchiha.
Hashirama was a tall man with tanned skin, brown eyes and long black hair typically styled in a centre-parted fringe that framed his face, although sometimes he wore it combed-back with two single locks framing his face instead. In most cases, his attire took the form of the standard shinobi dress of his era, consisting of dark red traditional armour — similar to that of samurai — worn over a simple black suit. This armour was constructed from numerous metal plates, formed into multiple protective guards along his body, in particular: chest, shoulders, thighs and forearms. Each collar of his shoulder guards bore the Senju symbol emblazoned on them. This clothing was accompanied by sandals and his village's forehead protector, after its formation. During battle, he also often carried a number of large scrolls.
While in the village, Hashirama tended to wear the traditional Kage attire consisting of the customary hat and cloak over a full-length gown, along with a simple red headband. Otherwise, he wore a light-brown, short-sleeved, kimono shirt with mesh armour underneath, held closed by a red sash, and navy blue pants.
Hashirama Senju is considered by many as the most powerful shinobi of his time. He was greatly respected by most shinobi during his lifetime, such that Tobi claimed Hashirama was the one person whom he respected the most as well as detested. Kabuto noted that Hashirama was stronger than Madara Uchiha and that his might was so vast, that there weren't any shinobi in the current era that could match his level of power. He also stated that many considered his prowess to be a mere fairy tale much like the existence of the Sage of the Six Paths. His prowess and abilities were so great that he was able to not only fight on equal footing with Madara Uchiha despite his power of Eternal Mangekyō Sharingan and having Kurama, the Nine-Tailed Demon Fox, at his side, but even gained victory in the end and survived the battle.
He knew how to perform a great number of techniques and was otherwise knowledgeable of those he could not. During his battle against his former student Hiruzen, he showed considerable taijutsu skill, able pressure the Third Hokage with it. In the manga, he also showed great genjutsu prowess, using the Bringer-of-Darkness Technique that covered the area in darkness which even Hiruzen couldn't dispel.
He was most famous for his unique Wood Release techniques, a kekkei genkai that is a mixture of earth and water-natured chakra that creates this new element. By converting chakra into the source of life, he was able to create trees, causing them to grow to great sizes and manipulate them to diverse shapes and battle uses at will. It was said that this ability was used to create the very landscape and foundation that Konoha is built upon. This ability appeared to be exclusively his, as no other known member of his clan has ever displayed its use. Even those who obtained this power through unorthodox means, such as Yamato, stated that his use of Wood Release was much weaker in terms of raw power. He could create massive forests, or create gigantic flowers which were able to put targets to sleep. In an instant, he could shape the entire battlefield for his own uses.
Along with his kekkei genkai, Orochimaru also coveted Hashirama's unique ability to control tailed beasts. Of all his considerable talents, it was this ability in particular that made Hashirama unparalleled in the shinobi world, so much so that he is regarded as one of the few people capable of completely controlling a tailed beast. At one time, he had many of the beasts in his possession. This ability was greatly amplified by his crystal necklace, which Yamato suggested that he required to control even Naruto's partial lapses into tailed forms.
- 'Hashirama' (柱間) is a Japanese word referring to the space between two pillars. This might be a play on the word 'pillar' (柱, hashira), as the Hokage is said to be the pillar that supports the village. '柱' is also the counter word for gods and buddhas.