The Senju clan (千手一族, Senju Ichizoku) was a group of shinobi that were the strongest, feared and most respected clan above all other clans in the ninja world during the war-torn era before the founding of the hidden villages. Together with their rivals — and distant relatives through a common ancestor — the Uchiha clan, they are responsible for founding the first hidden village named Konohagakure and making the village into what it is today. The clan has produced three of the five Hokage of Konoha: the First, Second, and the Fifth.
The Senju clan descended from the younger of the two sons of the Sage of the Six Paths who was born with the "body" of the Sage, inheriting his father's strength of will and physical energy and believed that love was the key to bringing peace to the world. The Sage grew to favour the ideals of his younger son over those of his older son, who believed that power alone was the true key to finding peace. Therefore, on his deathbed it was the younger of the two brothers that the Sage chose to name as his successor. The elder brother, bitter and hateful at having being denied what he felt was rightfully his to inherit, attacked his younger sibling. The Uchiha clan would descend from the elder brother, resulting in the bitter centuries-long rivalry between the Senju and the Uchiha. While undisputed, the Senju's legendary rivalry with Uchiha clan was taken advantage of by countries that hire their services. The Senju clan gained their fame in the era before the founding of the hidden villages. Where other clans focused on mastering one particular set of skills, the Senju were prodigious in all skills, from ninjutsu, to taijutsu, and genjutsu. Because of this, they were known as "the clan with a thousand skills" (「千の手を持つ一族」, "sen no te o motsu ichizoku"), which gave them their name "Senju" (千手; Literally meaning ""a thousand skills", "a thousand hands"").
The Senju clan under Hashirama's leadership. The most famous member of the clan was Hashirama Senju, whose unique Wood Release ninjutsu that gave the clan the nickname the Senju clan of the forest (森の千手一族, Mori no Senju Ichizoku), and his ability to control the tailed beasts, made him the greatest shinobi of his time. However, living in a world of constant bloodshed, Hashirama had a great love for his fellow man and a dream of peace among all ninja. Known as the "Will of Fire" (火の意志, "Hi no Ishi"), this belief enable Hashirama to use his position as leader to convince his clan to propose a truce with the Uchiha clan. Weary of fighting, and persuaded by Hashirama's great charisma and negotiation skill, though not accepted at first, the Uchiha ultimately conceded to the fact that the Senju were superior to them and started to surrender to the Senju. During a battle that lasted an entire day, Madara Uchiha finally fell in battle but still refused to accept the truce until Hashirama killed either himself or his own brother. Witnessing Hashirama's resolve to kill himself, Madara finally accepted their truce thus ending the bloody rivalry between the two clan.
The Senju and Uchiha form an alliance. The Senju and the Uchiha created a permanent settlement for shinobi within the country: Konohagakure. The first of its kind, the system along with the name inspired more countries to have their own hidden village per country, ending the Era of the Warring States with Hashirama's dream becoming a reality. But it would soon start again after Hashirama was elected as the First Hokage with the only Uchiha who was against the truce, Madara Uchiha who came to the conclusion that the hope for his clan was slowly dwindling, defected from the village in search of what he called his own reality. This would renew his battles with Hashirama until the fated, final battle at the Valley of the End where Hashirama resolved to protect his own dream, killing his former friend who had succumbed to the Curse of Hatred.
The Uzumaki and Senju. The Senju and Uzumaki clans are distant blood relatives whom they retained strong connections with. For this reason Konoha-nin uniforms have the symbol of Uzushiogakure emblazoned on its shoulders. Hashirama's wife would also come from this clan, further strengthening their ties. Throughout the years, the Senju retained their supremacy over Konoha, and made the village into what it is today. After the First Hokage's death, his younger brother, Tobirama Senju, stepped up to become the Second Hokage. Although likely not a Senju by blood, Hiruzen Sarutobi, who would become the Third Hokage after the Second's death, was trained by both the First and Second. His successor, Minato Namikaze, was the student of Jiraiya, who was a student of the Third. Tsunade, the Fifth Hokage, was not only a student of the Third, but also the granddaughter of the First and the grandniece of the Second. All of them strongly held to the Will of Fire philosophy. It is unknown if the Senju clan still exists as an independent clan since there are no known persons with the last name "Senju" — with the Fifth Hokage, Tsunade, being the only possible exception. Their legacy however, lives on strongly in the hearts of the people of Konoha.