The Byakugan (白眼, lit. White Eye; Viz: All Seeing White Eye) is the dōjutsu kekkei genkai of the Hyūga and Ōtsutsuki clans. It is regarded as one of the "Three Great Dōjutsu", the others being the Sharingan and the Rinnegan.
This dōjutsu usually is manifested as very distinctive eyes, characterised by their enlarged and featureless white irides (though the anime tends to portray them as a light shade of lavender) with no visible pupils. While active, the pupils become more distinct and the veins near their temples bulge. Unlike other dōjutsu, the Byakugan is normally available to its users from birth, and on rarer occasions, the dōjutsu can be awakened. Himawari Uzumaki, a descendant of the Hyūga clan through her mother, generally has blue eyes. When her Byakugan is activated, she gains the characteristic white, featureless eyes of her ancestors.
In the novel adaptation, it was shown that a Hyūga descendant of a more diluted bloodline may end up only awakening this dōjutsu in a single eye.
The Byakugan's abilities have left it highly coveted, as evidenced by other villages' attempts to steal it; Kumogakure used various machinations to obtain a Byakugan during the "Hyūga Affair". Ao of Kirigakure is the only foreign power known to have obtained a Byakugan from a Hyūga he defeated and he goes to great lengths to protect it; when Danzō Shimura, a loyal extremist of Konoha, finds out about this, he goes to similar lengths to retrieve or destroy it. Unlike other dōjutsu, transplanted Byakugan can be activated and deactivated at will. In order to reduce the probability of their eyes falling into enemy hands, the main house of the Hyūga place cursed seals onto the foreheads of branch house members which, among other things, seals away the Byakugan upon their death.
In the manga, after absorbing Kinshiki Ōtsutsuki's power, Momoshiki Ōtsutsuki's Byakugan takes a gold colour.