Amaterasu is the highest level Fire Release technique,and is noted to be Itachi Uchiha's strongest ninjutsu which stems from his dōjutsu. It is said to represent the "Material World and Light" (物質界と光, Busshitsukai to Hikari), the antipode to Tsukuyomi — a genjutsu of similar power and a fellow Mangekyō Sharingan dōjutsu. Use of the technique puts a great deal of strain on the user, usually causing his eyes to bleed.
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 Armourenhanced Body Flicker Technique avoided a short-range Amaterasu launched at him by Sasuke in an instant.
The flames are capable of burning through mostly 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'schakra-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. Jiraiya was also able to seal the flames with the Fire Sealing Method.
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