Amaterasu

Amaterasu is the highest level Fire Magic spells, and according to Zetsu, the strongest ninjutsu of Itachi's eyes. It is said to represent the, the antipode to Tsukuyomi, a genjutsu of similar power and a fellow Mangekyō Sharingan dōjutsu.

The jet-black flames of the Amaterasu, said to be the fires from hell that are as hot as the sun, ignite at the focus of the user's vision. Though the flames have been stated to be unavoidable, Amaterasu has been avoided a few times; Sasuke Uchiha managed to dodge the flames when Itachi tried focusing on him, though Itachi did not actually want to kill him and managed to hit Sasuke shortly after regardless, and A using his Lightning Release Armour enhanced Body Flicker Technique avoided a short-range Amaterasu launched at him by Sasuke in an instant.

The flames are capable of burning through most anything in their path, even smothering regular fire techniques with ease. Amaterasu is said to never stop burning; even when whatever is caught by the Amaterasu is completely reduced to ash or destroyed, it can still continue burning for seven days and seven nights. It cannot be extinguished with water or any other normal methods. The only thing that the flames have failed to burn into or through is Gaara's chakra-infused sand. However, the flames burn fairly slowly, sometimes allowing anyone struck by Amaterasu an opportunity to remove whatever clothing or body parts have been caught ablaze. Nagato was able to deflect the flames from his body using Shinra Tensei. Use of the technique also puts a great deal of strain on the user, usually causing their eyes to bleed.

Itachi Uchiha, who used it with his right Mangekyō Sharingan, is able to quell the flames to some extent. Prior to his death, Itachi implanted some of the black flames into Sasuke's eye which activates upon seeing Tobi's Sharingan. Sasuke, after gaining his own Mangekyō Sharingan, is later able to use Amaterasu on his own. Sasuke's Amaterasu originates from his left eye however, and C indicates he is more skilled with it than Itachi; he can put out the flames with greater ease and can even manipulate the flames themselves as part of the "Blaze" element.

Influence
As from the ancient Japanese myth and religion of Shintō, Amaterasu, Tsukuyomi, and Susanoo are all gods. When Izanagi washed his face after escaping the underworld his left eye became the Sun Goddess, Amaterasu.

Trivia

 * Despite the black flames being inextinguishable, both Sasuke and Tobi had somehow disposed of the black flames.