Yūki Hideyasu (結城秀康?), March 1, 1574 - June 2, 1607, was a daimyo of the Azuchi Momoyama and early Edo period. Second son of Ieyasu Tokugawa, he created the Fukui estate in Echizen province.
Hideyasu born Tokugawa Ogimaru in 1574, was the second son of Ieyasu Tokugawa, with his concubine Oman (also known as Lady Kogō). It is said that Oman gave birth to twins and that Ogimaru's brother succeeded Oman's father as priest of the Chiryū Tomb of Mikawa Province. He was born near Hamamatsu Castle in the village of Ofumi.
Oman was the servant of Lady Tsukiyama, Ieyasu's first wife. After getting her pregnant, fearing Tsukiyama's anger, Ieyasu hid her in Honda Shigetsugu's house. It is in this house that Ogimaru and his brother were born.
For an unknown reason the young Ogimaru is not loved by his father. When his half-brother Matsudaira Nobuyasu committed suicide, he should have been his father's heir, however during the peace negotiations that followed the battle of Komaki and Nagakute, he was adopted (in reality given as a hostage) to Hashiba Hideyoshi.
He then took the name of Hashiba Hideyasu, combining the names of his adoptive and biological fathers.
Hideyasu participated in the Kyūshū campaign in 1587, leading the assault on Buzen-Iwaishi Castle. He also received honors for his leadership of the pacification of Hyūga province.
Hideyasu participated in the siege of Odawara (1590) and the Korean campaign (1592). His successes in these campaigns earned him respect as a capable commander, despite his young age.
In 1589, born a son of Hideyoshi Toyotomi, Hideyasu was then adopted the following year by Yūki Harutomo of Shimōsa province.
After the battle of Sekigahara, he received in place of his fiefdom from Yūki's family in Shimōsa province (valued at 101,000 koku) that of Fukui (670,000 koku). In 1604, he took the surname of Matsudaira. When he died in 1607, his first son Matsudaira Tadanao succeeded him.