Lifespan: 3/15 of Tenshō 4 (1576) to 8/18 of Kanei 9 (1632)
Title: Junior Fifth Rank (Lower), Governor of Shinano, Junior Fourth Rank (Lower)
Lord: Toyotomi Hideyori → Tokugawa Ieyasu → Tokugawa Hidetada → Tokugawa Iemitsu
Father: Nanbu Nobunao
Mother: Daughter of Izumiyama Furuyasu
Siblings: Toshinao, Chiyo, Sueko
Wife: [Formal] Daughter of Gamō Ujisato (Takehime); [Consorts] Younger sister of Yamada Kurōzaemon (Hōgenin), younger sister of Ishii Naoya (Gakujo), Senjuin, daughter of Imabuchi Masaaki, Osanze
Children: Ienao, Masanao, Shigenao, Toshiyasu, Shigenobu, Toshinaga, Naofusa, Shichihime, Kita Naochika, daughter (wife of Higashi Tanemasa)
Adopted Children: Toshihiro
Nanbu Toshinao served as a daimyō during the Azuchi-Momoyama and early Edo periods. He was the first lord of the Morioka domain in Mutsu Province. Toshinao served as the twenty-seventh head of the Nanbu clan (the second head of the Morioka-Nanbu). He had the common name of Hikokurō.
In 1576, Toshinao was born as the eldest son of Nanbu Nobunao, the twenty-sixth head of the clan at Takko Castle in Sannohe. In 1590, Toshinao attended his coming-of-age ceremony and Maeda Toshiie served in the honorary role to place black-lacquered headgear known as an eboshi on Toshinao. On this occasion, he received one of the characters from the name of Toshiie and adopted the name of Toshimasa which he later changed to Toshinao. In 1595, he was invested with the title of Junior Fifth Rank (Lower) and Governor of Shinano.
After the death of Toyotomi Hideyoshi n 8/18 of Keichō 3 (1598), together with his father, Nobunao, Toshinao approached Tokugawa Ieyasu, the leader of the Council of Five Elders. In 1599, his father died so he inherited the headship of the Nanbu family. In 1600, at the Battle of Sekigahara, Ieyasu of the Eastern Army ordered the daimyō in the Tōhoku and Hokuriku regions to subjugate Uesugi Kagekatsu in Aizu who was colluding with Ishida Mitsunari of the Western Army. With the backing of Mogami Yoshiaki, Toshinao deployed to Yamagata for the Battle of Keichō Dewa. Meanwhile, in a secret plot to expand his territory, Date Masamune instigated uprisings in the Waga and Hienuki districts by Waga Tadachika so Toshinao was permitted to return to Mutsu and, by 1601, suppressed the Waga forces. This event is known as the Iwasaki Uprising.
Thereafter, Toshinao initiated the governance of the Morioka domain. After being dispatched by the domain to northern Mutsu to inspect the border with the territory of Akita Sanesue, a retainer of Toshinao named Kita Nobukage discovered the Shirane kinzan – a gold mine. Mining operations at this site and at the Saidō kinzan generated income to secure the finances of the domain. After a while, the domain achieved significant amounts of wealth supporting the development of an early-modern form of governance. In 1615, Toshinao constructed Morioka Castle and the town below while the residents living below Sannohe Castle moved to Morioka. Moreover, in the wake of the Revolt of Kunohe Masazane, Toshinao consolidated adjudicatory powers, punishing or expelling many retainers, solidifying the foundation of the Morioka domain.
In 1614, Toshinao served in the Winter Campaign of the Siege of Ōsaka and strengthened relations with the Edo bakufu. In 1626, he was promoted to the title of Junior Fourth Rank (Lower).
On 8/18 of Kanei 9 (1632), Toshinao died at the Sakurada residence in Edo at the age of fifty-seven. He was succeeded by his third son, Nanbu Shigenao. Later, Shigenao died without a son, so the Morioka domain was divided between Toshinao’s fifth son, Nanbu Shigenobu, and his seventh son, Nanbu Naofusa (the founder of the Hachinohe domain).