Mashita Nagamori (増田 長盛, 1545 – June 23, 1615) was a daimyō in Azuchi–Momoyama period, and one of the Go-Bugyō appointed by Toyotomi Hideyoshi.

Nagamori was born in Nakashima-no-kori, Mashita-mura, Owari Province or Asai-gori, Mashita-go, Ōmi Province and served Hashiba Hideyoshi (Toyotomi Hideyoshi) when he had been a retainer of Oda Nobunaga.

After Hideyoshi died, in 1600, Nagamori took part in Ishida Mitsunari's force when he put up Mōri Terumoto who was a member of the council of Five Elders and raised their army to Tokugawa Ieyasu.

He did not take part in the Battle of Sekigahara on October 21, but rather held a fort at Osaka Castle.

In 1615 at the Siege of Osaka, Nagamori's son Mashita Moritsugu, who had served Tokugawa Yoshinao, escaped and joined the Toyotomi Clan's force.