Itachi Uchiha (うちは イタチ ,Uchiha Itachi) is a former ninja of Konohagakure and the partner of Kisame Hoshigaki. Though having spent his early youth as the kindly child prodigy of the Uchiha clan, Itachi is treated as a villain for much of the series. He is initially portrayed as being solely responsible for the slaughter of his entire clan and family, sparing only his brother, Sasuke Uchiha, with the explanation that he was testing his abilities. Around the time of his death his villainous role is downplayed; not only is he revealed to have had help from Madara Uchiha, in killing the clan, but he performed the massacre under the orders of Konoha's leadership so as to prevent an Uchiha coup d'état. Though he was ordered to kill Sasuke as well, Itachi could not bring himself to do so, instead forcing Konoha to keep Sasuke safe or risk Itachi going public with his mission. For his part, Itachi accepts his role as a villain, never telling anyone of who else was involved and even encouraging Sasuke to grow strong enough to kill him and avenge their family.

Throughout the series Itachi attempts to avoid combat, seeking nonviolent solutions instead. If he is forced to battle he usually remains stationary, only acting in self-defense. From his idle position he studies an opponent's movements with his Sharingan eyes, trapping them in illusions when opportune by merely pointing or looking at them. Itachi at times uses one of the three abilities of his Mangekyo Sharingan, though he tries to avoid doing so as it is taxing on his body and damages his eyesight. The first, Tsukuyomi (月読 ?), allows him to torture opponents for what seems like days in a matter of moments. Amaterasu (天照 ?), the second, generates black flames at his focal point that will continue to burn until the target is reduced to ash. The final ability, Susanoo (須佐能乎 ?), creates a massive ethereal warrior that fights on Itachi's behalf, shields him from all attacks and wields a sword that is able to cut through anything. Before he purposefully dies during his battle with Sasuke, Itachi implants his Amaterasu in Sasuke's eyes, hoping that doing this will keep him safe from Madara Uchiha. All three attacks are named after Japanese celestial gods; the gods of moon, sun and storm, respectively. In the Japanese anime, Itachi's seiyū is Hideo Ishikawa. His first voice actor in the English anime was Skip Stellrecht, who voiced Itachi in episodes 29 and 30, but in all following appearances, he has been voiced by Crispin Freeman.

Source: Wikipedia