Izuna Uchiha (うちはイズナ, Uchiha Izuna) was a shinobi of the Uchiha clan. He, along with his brother Madara Uchiha, were renowned as the clan's two strongest members in their lifetime.
Izuna was a fair-skinned man with spiky, black hair that had a blue tint to it and was tied in a ponytail. His bangs parted down the centre of his face to frame both sides of it. He wore the standard Uchiha outfit which consisted of a high-collared, blue shirt with the Uchiha crest on his upper back and blue pants which were wrapped up in bandages at the ends. On his waist, he had a bandage belt that held a sack which presumably held ninja tools. As a child, his ponytail was absent, and his hair was spiky in the back, and he wore the standard high-collared robes worn by other Uchiha of the Era of the Warring States with the Uchiha crest on the back, with an armored chest plate. According to Hashirama Senju, Izuna bore a striking resemblance to one of his descendants, Sasuke Uchiha.
Izuna Uchiha was a harmonic and devoted person. He was very competitive with his brother, Madara, in terms of skill as they would often spar with one another in an attempt to hone these skills. Izuna looked up to Madara greatly and was even in disbelief when as children, Madara admitted to being weaker than Hashirama. Likewise, Izuna was elated when Madara awakened his Sharingan shortly after. As he grew older, Izuna's love for his clan grew and he fought fiercely to protect it. He soon came to share his clan's opinion regarding the Senju clan, even asking Madara, while severely wounded, not to fall for Hashirama's "false" truce proposals. He looked up to his older brother and was so close to Madara that he even gave him his eyes as a dying gift as a means of ensuring that Madara will be able to better protect the clan's future.