Name: Uchiha Itachi
Age: 17-18 (I); 21 (II)
Birthday: June 9th
Height: 175 cm (I); 178 cm (II)
Weight: 57 kg (I); 58 kg (II)
Blood Type: AB
Nature Type: Fire and Water
From: Konohagakure (Leaf)
Rank: S-class Missing-Nin
Registered Ninja #: 012110
Ring: Shu (Red)
Finger Position: Right Ring
Partner: Hoshigaki Kisame
Favorite Foods: Rice balls (kelp), cabbage
Least Favorite Foods: Steak
Hobby: Visiting traditional Japanese cafés
First Manga Appearance: Ch. 139
First Anime Appearance: Ep. 80
Assignments Completed: 53 D-Rank, 152 C-Rank, 134 B-Rank, 0 A-Rank, 1 S-Rank
Famous Quote: Foolish little brother, if you wish to kill me, hate me, detest me, and survive in an unsightly way. Run, run and cling to life.
When the Uchiha began planning to overthrow Konoha, Itachi, as an ANBU, was tasked with spying on the village. Knowing that a coup d'etat would only lead to another Ninja War, Itachi chose to spy on the Uchiha instead, passing on information to the Third Hokage and the other Konoha elders. After this he began to act strangely, not attending the clan meetings, speaking out against the clan, and becoming the prime suspect for the murder of his best friend, Shisui Uchiha. The clan lost hope in Itachi, and his father began shifting his focus to Sasuke instead. Meanwhile, the Third's attempts to negotiate a bloodless end to hostilities between the two parties were proving ineffective, so, against the Third's wishes, Danzo and the Konoha Council ordered Itachi to wipe out the Uchiha. Before the fateful night arrived, Itachi discovered the existence of Madara Uchiha, who was attempting to rekindle the flames of war in Konoha. In return for not attacking Konoha, Itachi offered to help Madara claim vengeance against the Uchiha for turning their backs on him decades earlier. Madara agreed. Itachi slaughtered his entire clan overnight, sparing only Sasuke. Sasuke's life was worth more than the village to Itachi, and he could not follow through with the orders to kill him as well. Instead, he made himself out as a villain, who had killed their innocent family only to test his abilities. By doing so, he wanted Sasuke to take vengeance on him and become a hero to Konoha, thus redeeming the Uchiha name. He tortured Sasuke with his Mangekyo Sharingan, and encouraged him to become strong enough to kill him and avenge their family. Hoping that his beloved little brother would someday be powerful enough to kill him, Itachi left the village as a traitor. Knowing that Konoha would still want to eliminate Sasuke, Itachi pleaded with the Third Hokage to keep Sasuke safe. He also threatened Danzo to not harm Sasuke or risk him revealing everything he knew about Konoha's secrets to enemy countries. Sasuke's safety was therefore secured, and Itachi returned to his original plan of becoming infamous for his slaughter of the Uchiha. Itachi joined Akatsuki in order to keep an eye on the organization, along with Madara Uchiha, in case either ever acted against Konoha, all the while planning for his death at Sasuke's hands. While a member of Akatsuki, Itachi was approached by Orochimaru, who tried to steal his body to gain the Sharingan. Itachi trapped him in a genjutsu and severed his left hand as punishment, forcing Orochimaru to flee the organization. Sometime after joining Akatsuki, Itachi later helped recruit Deidara, Orochimaru's replacement, by beating him in battle, after which Deidara swore vengeance again.
Despite his mastery of the Mangekyo Sharingan, Itachi suffered greatly from its side effects. His eyesight would worsen after every activation of the Mangekyo Sharingan, and he would eventually go blind from its power, with his Sharingan forever sealed away. Itachi was so close to blindness that, by the time he activated Susanoo in his final fight, both Sharingan eyes had become almost blind, and had turned white. However, he was still able to perform his own Fūinjutsu in his last moments.
(Sources: Naruto.com and Naruto.wikia.com )