Mashita Nagamori (増田 長盛; 1545 – June 23, 1615) is a daimyo in Azuchi-Momoyama period, and five bugyo appointed by Toyotomi Hideyoshi. Also called Niemon (仁右衛門) or Uemon-no-jyo (右衛門尉).

Nagamori was born in Nakasima-no-kori, Mashita-mura, Owari Province or Asai-gori, Mashita-go, Omi Province and served Hashiba Hideyoshi (Toyotomi Hideyoshi) when he had been a retainer of Oda Nobunaga. Since he shined with domestic affairs such as Cadastral Surveys by Hideyoshi and diplomatic negotiations with Uesugi Kagekatsu, Hideyoshi gave him 200,000 koku at Koriyama Castle, Yamato Province and appointed him to five bugyo. Nagamori took part in the Battle of Bunroku (in 1592) and the Battle of Keicho (in 1596).

After Hideyoshi died, in 1600, Nagamori took part in Ishida Mitsunari's force when he put up Mori Terumoto who was a five Tairo and raised their army to Tokugawa Ieyasu. However, Nagamori was involved in an intrigue with Ieyasu. He didn't take part in the Battle of Sekigahara on October 21 and held a fort at Osaka Castle. After the Battle, Ieyasu seized Nagamori's domain, but helped his life and left him to Koriki Kiyonaga who was an Ieyasu's retainer and lord of Iwatsuki Castle, Musashi Province.

In 1615 at Siege of Osaka, Nagamori's son Mashita Moritsugu , who had served to Tokugawa Yoshinao, escaped and took part in Toyotomi Clan 's force. In the result, Nagamori was commanded to commit suicide. He died at 71.

His grave is at Anraku-ji, Niiza, Saitama, Saitama Prefecture.