Udono Ujitsugu served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a member of the Imagawa clan and, later, a retainer of the Tokugawa clan.
Ujitsugu was born as the son of Udono Nagateru, a retainer of Imagawa Yoshimoto. Ujitsugu and his older brother, Udono Ujinaga, are surmised to have received one of the characters in their names from Imagawa Ujizane because they were blood relatives of the Imagawa clan.
In 1562, owing to an attack by Matsudaira Motoyasu (later known as Tokugawa Ieyasu), the base of the Udono clan at Kaminogō Castle was toppled and his father, Nagateru, and grandfather, Udono Nagamochi, died in battle. Meanwhile, Ujitsugu and his older brother, Ujinaga, were apprehended. In exchange for their return, Ieyasu demanded the release of his formal wife (Senahime or Tsukiyama-dono), his lineal heir (Takechiyo or Matsudaira Nobuyasu), and his eldest daughter (Kamehime) who were tendered as hostages to the Yoshimoto during the period that he was under the command of the Imagawa clan. Nagamochi’s formal wife was the younger sister of Yoshimoto so Ujinaga and the Udono family who loyally served the Imagawa family were close relatives of Imagawa Ujizane (the lord of the clan at the time).
The negotiations bore fruit and Ujitsugu was released to the Imagawa family. Having lost his homeland and own landholdings in Mikawa, he turned to Matsui Munetsune at Futamata Castle in Tōtōmi Province. In 1568, Ieyasu, acting in concert with Takeda Shingen, invaded the territory of the Imagawa and attacked Futamata Castle. After losing territory from the east and the west, the Imagawa collapsed. Ujitsugu surrendered to Ieyasu and thereafter served as a retainer. He was turned over to the custody of Matsudaira Ietada, a cousin and the lord of Fukōzu Castle.
In 1600, during the Siege of Fushimi Castle in the prelude to the main Battle of Sekigahara, Ietada was stationed at the castle as a lieutenant general for the defense of the castle. Ujitsugu was also at the castle but could not halt the surge of a large Western Army and he was killed in action.