was a samurai in Bakumatsu period Japan, and a close associate of Sakamoto Ryà Âma in the movement to overthrow the Tokugawa shogunate.
Nakaoka was born in Tosa Domain, in what is now the village of Kitagawa, Kà Âchi Prefecture, as the son of a village headman. In 1861, he enrolled in the academy run by Takechi Hanpeita where he studied swordsmanship. He was one of the founding members of the Tosa Kinno-tà Â, a paramilitary shishi organization created by Takeichi to support the sonnà  jà Âi movement. After the coup dâÂÂetat of September 30, 1863, led to the suppression of the sonnà  Jà Âi faction, he fled to Chà Âshà « Domain together with pro-Sonnà  Jà Âi nobles, including Sanjà  Sanetomi. In 1864, he participated in a failed plot to assassinate Shimazu Hisamitsu, and fought alongside Chà Âshà « forces during the Kinmon Incident and the Bombardment of Shimonoseki. Later that year, as a member of the Kaientai formed by Sakamoto Ryà Âma, he worked to bring about the Satsuma-Chà Âshà « Alliance and obtain the backing and support of Sanjà  Sanetomi for the project. In March, 1867, he travelled with Sakamoto Ryà Âma to their native Tosa Domain to negotiate a similar alliance between Tosa and Satsuma. In June, he began negotiations to further expand the new alliance to include Chà Âshà « as well as Hiroshima Domain, but the issue was rendered moot when shà Âgun Tokugawa Yoshinobu formally returned governing power to the Emperor. Realizing that civil war was now increasingly probable, Nakaoka returned to Tosa and established the Rikuentai militia. Rikuentai was modeled after the Kiheitai in Chà Âshà « in July.
On December 10, 1867, Nakaoka traveled to Kyoto for discussions with Sakamoto Ryà Âma, but was mortally wounded together with Sakamoto when unknown assailants attacked their lodgings (i.e. the "à Âmiya Incident"). Sakamoto died soon afterwards, but the critically injured Nakaoka lingered for two days, although never regaining enough consciousness to identify the attackers, though he did mention hearing Iyo dialect among the killers. His grave is located at the Ryosen Gokoku Jinja in Higashiyama-ku, Kyoto. He was posthumously awarded with the court rank of 4th grade in 1891 by Emperor Meiji.
There is a large bronze statue of Nakaoka Shintarà  at Murotomisaki lighthouse in Cape Muroto in his native Kochi Prefecture, and another (together with Sakamoto Ryà Âma) at Maruyama Park in Kyoto.