Lifespan: Eiroku 11 (1568) to 11/2 of Kanei 9 (1632)
Rank: bushō, daimyō
Title: Junior Fifth Rank (Lower), Chief of the Palace Table
Domain: lord of Shimōsa-Yamazaki, lord of Tanba-Kameyama, lord of Tanba-Fukuchiyama, lord of Mino-Ōgaki
Lord: Tokugawa Ieyasu → Tokugawa Hidetada → Tokugawa Iemitsu
Father: Okabe Masatsuna
Mother: Daughter of Miura Noritoki
Siblings: Nagamori, Masatsuna
Wife: Daughter of Matsudaira Kiyomune, Dōsenin (adopted daughter of Tokugawa Ieyasu)
Children: Kōgenin, Nobukatsu, 与賢, Nagamasa, Yoshimi, Sadanao, daughter (formal wife of Oda Nobunori), Kichi, daughter (formal wife of Terazawa Katataka)
Okabe Nagamori served as a bushō and daimyō from the Azuchi-Momoyama to early Edo periods. In the Edo period, Nagamori served as the lord of the Shimōsa-Yamazaki domain, the Tanba-Kameyama domain, and as the first lord of the Mino-Ōgaki domain. He was also the first head of the Okabe family of the Izumi-Kishiwada domain. Excelling in military arts, Nagamori was called “Okabe the Black Demon.”
In 1583, Nagamori was born as the eldest son of Okabe Masatsuna. Upon the demise of his father, Nagamori succeeded him as the head of the family. Under another theory, prior to Nagamori, another individual with the name of Yasutsuna or Tadatsuna served as the head of the Okabe family, but there is a division of opinion as to whether this refers to Nagamori or an individual who was his older brother.
In 1584, Nagamori participated in the Battle of Komaki-Nagakute and, in 1585, under the command of Torii Mototada, against Sanada Masayuki during the First Battle of Ueda in Shinano Province. In 1590, after Tokugawa Ieyasu was transferred to the Kantō, as recognition for his earlier contributions, Nagamori received a fief of 12,000 koku in Yamazaki in Shimōsa Province. In 1600, during the Battle of Sekigahara, Nagamori was assigned to defend Kurobane Castle in Shimotsuke Province in case of a southward advance by Uesugi Kagekatsu.
In 1609, Nagamori was transferred to Tanba-Kameyama and received a larger fief of 32,000 koku (later increased to 40,000 koku). In 1615, he contributed at the Summer Campaign of the Siege of Ōsaka and, in 1621, was transferred to Fukuchiyama with an increase of his fief to 50,000 koku. In 1624, he was subsequently transferred to Mino-Ōgaki with a fief of 50,000 koku.
In Kameyama, Nagamori made efforts to promote development across his territory, including projects to expand the castle and for flood control, the enactment in Fukuchiyama of a code of conduct with 31 provisions, and the construction of roads to subdivide landholdings in the town of Ōgaki.
On 11/2 of Kanei 9 (2632), Nagamori died at the age of sixty-five. He was succeeded by his eldest son, Okabe Nobukatsu.