Nasu no Yoichi (那須 与一, Nasu no Yoichi) (c. 1169 – c. 1232) was a samurai who fought alongside the Minamoto clan in the Genpei War. He is particularly famous for his actions at the Battle of Yashima in 1185. According to the Heike Monogatari, the enemy Taira placed a fan atop a pole on one of their ships, daring the Minamoto warriors to shoot it off. Sitting atop his mount in the waves, his target atop the ship rocking as well, Nasu nevertheless shot it down with only one shot.

After the Genpei War, he was made shugo of Tottori Castle, but he lost this position to Kajiwara Kagetoki after being defeated in a hunting competition. He left Echigo Province and—following the death of Minamoto no Yoritomo—Nasu became a Buddhist monk in the Jōdo Shinshū sect. Eventually, he formed a temple, which has since been passed down to the oldest son of the Nasu family. For administrative purposes, detailed records were kept regarding who was to inherit the temple. As a result of this, it was possible to trace the Nasu lineage right up to the destruction of the temple during World War II.

There is another legend that his death in 1189 (or 1190) was disguised to facilitate his escape from Yoritomo's purge, and that the reason for his becoming a priest was that his complexion had changed due to Hansen's disease. Meanwhile, according to Yoshisada Nasu, Yoichi was pardoned and returned to Nasu after Yoritomo's death, became a priest in order to enter the Jodo-shu sect and died from paralysis in 1232 in Settsu Province, after a journey of about 30 years mourning those who had died in the Battle of Gempei-Kassen.

Yoichi is a common name which denotes the tenth or eleventh son. Sanada Yoshitada and Asari Yoshito were contemporaries who also called themselves Yoichi. They and Nasu no Yoichi are collectively called the 'three Yoichi of Genji.'

Since the name of Nasu no Yoichi is not seen in historical materials of the same period such as Azuma Kagami (The Mirror of the East), Yoichi's achievements are mostly handed down in the war chronicles The Tale of the Heike and Genpei Seisuiki.

According to the description of the Tale of the Heike, he was born as a child of Nasu no Suketaka around the first year of Kao (1169), the first year of Eiman / the first year of Nin'an (1166), and the third year of Nin'an (1168). It is often assumed that the place of birth was Kanda-jo Castle (present Nakagawa-machi, Nasu County, Tochigi Prefecture) where the Nasu clan lived at that time.

In the Genpei War, he took the side of Minamoto no Yoritomo along with his brother Juro Tametaka, and joined the army of his younger brother, Yoshitsune. In the Battle of Yashima, he famously shot down the target of a fan on the Taira clan's warship, and was granted a shoen (manor in medieval Japan) over five provinces by Yoritomo.

His nine older brothers, except Tametaka, supported the Taira clan. Tametaka was later punished, and therefore, Yoichi gained the family estate of the Nasu clan, although he was the eleventh son. Yoichi pardoned his older brothers who had escaped to various places such as Shinano, gave them territory, and laid the foundation for the development of the Nasu clan in Shimotsuke Province.