Lifespan: 9/7 of Eishō 8 (1511) to 12/5 of Tenbun 4 (1535)
Rank: bushō; seventh head of the Anjō-Matsudaira clan of Mikawa
Father: Matsudaira Nobutada
Mother: Daughter of Ōkōchi Mitsunari
Siblings: Kiyoyasu, Nobutaka, Yasutaka, Hisa (wife of Suzuki Shigenao), Azuma-hime (wife of Ōhama Michiba), younger sister (wife of Kira Mochihiro)
Wife: Oharu (Haru-hime)
Children: Hirotada, Nobuyasu, Shunkeini (formal wife of Kira Yoshiyasu), Usui-hime (wife of Matsudaira Masatada → wife of Sakai Tadatsugu), Ohisa (adopted; wife of Matsudaira Norikatsu → wife of Suzuki Shigenao), Seto-no-Ōfusa (wife of Kira Mochihiro)
Matsudaira Kiyoyasu served as the seventh head of the Matsudaira clan of Mikawa Province (also known as the Anjō-Matsudaira clan). Kiyoyasu was the eldest son of Matsudaira Nobutada, the sixth head of the clan. Kiyoyasu served as lord of Anjō Castle and Okazaki Castle. He took control of disaffected retainers and family members to secure his position in western Mikawa. Kiyoyasu was the grandfather of Tokugawa Ieyasu.
The unification of Mikawa Province
In 1523, his grandfather, Matsudaira Nagachika, along with other family members, compelled Nobutada to retire, and supported Kiyoyasu as the next leader of the clan. Kiyoyasu received one of the characters in his name from Kira Tokukiyo of the Kira clan in Mikawa.
In 1525, Kiyoyasu attacked and forced the surrender of Suzuki Shigemasa at Mayumiyama Castle in the Kamo District of Mikawa. In 1526, he toppled Matsudaira Masayasu at Yamanaka Castle held by branch of the Matsudaira family based at Okazaki Castle. Kiyoyasu had the old castle destroyed, built a new castle on Mount Ryūzu, and re-located the Matsudaira clan to this location. The Matsudaira then built a town below the castle. To support the effort, Kiyoyasu established a system of governors and assistants,. along with the Okazaki goninshū, a group of five senior retainers who were accomplished in the military arts. Kiyoyasu arranged for the reconstruction of the Matsudaira family temple and pagoda at Daiju Temple, recognized by the Emperor as an official place of worship. He also constructed the Rokusho Shrine and the Ryūkai Temple.
In 1529, Kiyoyasu received support from the Tōjō-Kira clan to topple Arakawa Yoshihiro at Oshima Castle. Later that year, his forces proceeded to capture Imabashi Castle (later renamed Yoshida Castle) from the Makino clan in the Atsumi District of eastern Mikawa. Kiyoyasu forced the surrender of the Toda clan in the same district without a battle. At this time, a group of families in the Shitara District to the north, including the Suganuma clan based at Damine and Nagashino castles, and the Okudaira clan based at Kameyama Castle, in addition to others in the east including the Makino clan at Ushikubo Castle in the Hoi District, pledged their allegiance to the Matsudaira. Only the Kumagai clan based at Uri Castle in the Yana District on the eastern border of Mikawa refused to surrender, whereupon the Matsudaira surrounded and captured their base. Kiyoyasu nearly completed the pacification of Mikawa Province.
According to one account, Kiyoyasu had a falling out with his uncle, Matsudaira Nobusada from the Sakurai-Matsudaira family. This followed the loss of his uncle, Matsudaira Chikamori of the Fukama-Matsudaira family, who died in battle near the front entrance of Uri Castle owing to a delay in reinforcements under the command of Nobusada. The scorn from Kiyoyasu may have caused Nobusada to harbor animosity toward Kiyoyasu as well as a desire to overthrow him as head of the clan.
In 1530, the Matsudaira re-entered Owari Province, captured Iwasaki and Shinano castles, and raided the surrounding villages. In the wake of pacifying Mikawa, Kiyoyasu marched toward Owari with an army of over 10,000 men. Late in 1535, Kiyoyasu invaded Owari and attacked Moriyama Castle, defended by Oda Nobumitsu, the younger brother of Oda Nobuhide. While Kiyoyasu was near the main gate of the castle, Abe Masatoyo, one of his retainers, suddenly cut-off his head. Masatoyo was in turn immediately slayed by Uemura Ujiaki. This incident is known as the Moriyama kuzure, or the Collapse at Moriyama. Kiyoyasu perished at the young age of twenty-five. The unexpected loss of Kiyoyasu caused a loss of momentum and subsequent trouble for the Matsudaira clan.