The Mizuno clan (水野氏 Mizuno-shi) was a clan of daimyō in feudal Japan who claimed to be descended from Minamoto no Mitsumasa and thus Seiwa Genji.
Shigefusa, a descendant of Mitsumasa, settled in Owari Province, where the family would remain for many years.
Shigefusa's son, Shigekiyo, helped Minamoto no Yoritomo during the Gempei War (1180-85) and was later transferred to Mizuno, also in the Owari. Shigekiyo's son, Kiyofusa, first assumed the name of Mizuno.
During the Sengoku period the Mizuno were involved in the often convoluted struggle for power on the Tokai coast, and alternately supported the Imagawa, Matsudaira and Oda clans.
They became a servant family of the Tokugawa after 1560, only to later serve the Toyotomi. After the Battle of Sekigahara (1600), having sided with Tokugawa Ieyasu, they maintained daimyō status with the Tokugawa shogunate.
Important Mizuno clan members
- Mizuno Tadamasa (水野 忠政; 1493-1543) later conquered the castles of Okawa (Owari), Otaka (Owari), and Kariya (Mikawa). He rebuilt the castle of Kariya in 1533. He was the father of Odai no kata, wife of Matsudaira Hirotada and mother of Tokugawa Ieyasu.
- Mizuno Nobumoto (水野 信元; 1506-1576) Son and heir of Tadamasa. Received the title Shimotsuke no kami, in 1543 he abandoned the Imagawa, of whom he was a vassal, to follow Oda Nobuhide; this alienated the Matsudaira and Tokugawa from him until the day they all united around Oda Nobunaga. After an argument with Sakuma Nobumasa, Nobumoto was accused by Nobunaga who ordered Ieyasu to put him to death: Ieyasu obeyed and sent his uncle's head to Nobunaga.
- Mizuno Tadashige (水野 忠重; 1541-1600) Son of Tadamasa and brother of Nobumoto, upon the latter's death he was chosen as heir to his castle at Kariya (Mikawa). He served Toyotomi Hideyoshi, who awarded him the title Izumi no kami and increased his income to 40,000 koku. He was assassinated by Kaganoi Shigemochi during a dispute just before the Battle of Sekigahara.Mizuno Katsushige (水野 勝成; 1564-1651) Son and heir of Tadashige. Participated in the Kyūshū campaign (1587) under the leadership of Sassa Narimasa. During the Japanese Invasions of Korea (1592-1598) his conduct was disgraceful. He moved from the army of Konishi Yukinaga to that of Katō Kiyomasa, then to that of Kuroda Nagamasa, Miura Shigekatsu, etc.. Back in Japan he sided with Ieyasu, his cousin, and was given the title of Hyūga no kami. In 1615 he was transferred from Kariya to Koriyama (Yamato - 60,000 koku) In 1619 to Fukuyama (Bingo - 100,000 koku). In 1638, he helped suppress the Shimabara revolt. In 1646, he had his head shaved and took the name Sōkiū. His direct lineage ended in 1698. An heir was chosen for him in the person of one of his relatives, who in 1703 received the castle of Yuki (Shimōsa - 17,000 koku) where they remained until the Meiji renewal.