Nikkō (日興) (1246-1333), also known as Nikkō Shōnin, is the founder of a major branch of Nichiren Buddhism that includes the present-day Nichiren Shoshu school of Japanese Buddhism.

On October 8, 1282, Nikko was designated by Nichiren as one of the principal disciples (later known as the six elders) to carry on his faith. On October 13, Nichiren designated Nikko the chief priest of Kuonji, the temple at Mt. Minobu where Nichiren spent the last years of his life. Nichiren passed away later on the same day at Ikegami, now part of Tokyo.

Nikko then claimed that, as well as appointing him chief priest of Kuonji, Nichiren had designated Nikko his sole successor as leader of the school, and he produced a document dated the ninth lunar month of 1282 (Nichiren ichigo guhō fuzoku-sho, "Document assigning all the teachings spread by Nichiren during his lifetime") to back this up. The claim was rejected by the other five disciples, and Nichiren Buddhism split into the branches stemming from Nikko and the sects, most amalgamated in today's Nichiren Shu, stemming from the other five disciples.

In the spring of 1289 Nikko, carrying the Dai-Gohonzon (the object of worship Nichiren had left behind; see Nichiren Shoshu ), Nichiren's ashes, and a number of other relics, left Mt. Minobu with his disciples. Nanjo Tokimitsu, a lay believer residing near Mt. Fuji in today's Fujinomiya, donated a tract of land for a new temple that became Taisekiji. Taisekiji is today the head temple of the Nichiren Shoshu school and, since its founding on October 12, 1290, has always been a major center of the Kōmon and later Fuji branches of Nichiren Buddhism.

Nikko became Nichiren's disciple sometime between 1258 and 1260—the precise date is unknown. His full Buddhist name was Hawaki-bō Byakuren Ajari Nikkō (伯耆房 白蓮阿闍梨 日興). He served Nichiren closely from then until the latter's passing, even accompanying Nichiren on his two exiles. Nikko was a master calligrapher as well as well versed in Japanese poetry and Chinese literature, and he is credited with preserving many of Nichiren's voluminous writings. He was particularly careful to ensure the survival of Nichiren's many letters written in simple language for uneducated followers.

After his involvement with the founding of Taisekiji, Nikko named his disciple Nichimoku (1260–1333) as his successor and retired a few miles away to Omosu, where he founded a seminary and concentrated on training disciples until his passing in the second lunar month of 1333 at the age of 87.

Sources

• Nikkō Shōnin Nichimoku Shōnin Shōden (日興上人･日目上人正伝: "Orthodox biography of Nikko Shonin and Nichimoku Shonin"), Taisekiji, 1982
• Nichiren Daishōnin Shōden (日蓮大聖人正伝: "Orthodox biography of Nichiren Daishonin"), Taisekiji, 1981
• The Life of Nichiren Daishonin. Kirimura, Yasuji. Nichiren Shoshu International Center (no longer connected to to Nichiren Shoshu), 1980