Uchiha klanı (うちは一族, Uchiha Ichizoku) Konohagakure'nin dört soylu klanından biridir, reputed to be the village's strongest because of their Sharingan and natural battle prowess. After helping found Konoha decades ago, the Uchiha grew increasingly isolated from the village's affairs, culminating in most of their deaths during the Uchiha Clan Downfall. Few Uchiha now survive into the present day.
The Uchiha are descendants of Indra Ōtsutsuki, the elder son of Hagoromo Ōtsutsuki. Through Indra, the Uchiha inherited Hagoromo's "eyes", granting them powerful spiritual energy and chakra. As part of the so-called "Curse of Hatred" first displayed by Indra, Uchiha are subject to powerful emotions: these emotions typically start as love for a friend or family member that then become overpowering hatred when the object of their love is lost. This loss, whether actually experienced or merely threatened, awakens an Uchiha's Sharingan. It is due to the Sharingan that the Uchiha have received much of their fame and notoriety.
The Uchiha have been fighting the Senju clan for centuries, a rivalry that traces back to the days of Indra and his younger brother, Asura. When the Sage of Six Paths was dying, he selected Asura as his successor, believing Asura's desire for peace through love was better than Indra's peace through power. Indra, driven by his Curse of Hatred, fought Asura to claim what he believed was his birthright. The Uchiha and Senju, descendants of Indra and Asura respectively, continued their battle through the centuries, though none still remembered this reason for their conflict.
By the time of the Warring States Period, the Uchiha and Senju had emerged as the strongest shinobi clans in the world. When one of the fledgling countries of the era would hire the Uchiha to fight in their wars, the opposing side would hire the Senju. The constant warfare between their clans only fueled their hatred, with all Uchiha owing the death of a loved one to an Senju and vice versa. But centuries of conflict began to wear on members of the clans; Madara Uchiha and Hashirama Senju met as children and became friends, bonding over their disapproval of the combat and death that they and their younger brothers were constantly subjected to and dreaming of a time when children wouldn't need to fight. Unable to do anything about the world at their age, Madara turned away from their dreams.
Madara and Hashirama continued to face each other in battle over the coming years. Driven by his desire to defeat Hashirama and through competition with his younger brother, Izuna, Madara became the first Uchiha to awaken his Mangekyō Sharingan. With its increased power he took control of the Uchiha. Hashirama, by then leader of the Senju, tried to use their positions to broker peace between them and finally achieve their childhood dreams. Despite growing interest in peace amongst the Uchiha, Madara was unwilling to agree to peace after Izuna was killed by Hashirama's brother, Tobirama. Using Izuna's eyes to acquire "eternal" Mangekyō, Madara challenged the Senju for supremacy one final time. He was defeated, but even then refused Hashirama's offer of peace, insisting that Hashirama kill himself first. When Hashirama agreed to these terms, Madara was moved to accept, withdrawing his request for Hashirama's death.