Lifespan: Unknown to 2/22 of Keichō 19 (1614)
Other Names: Chikakatsu, Yorikatsu, Harushige, Seiemon
Bakufu: Edo — hatamoto
Lord: Matsudaira Hirotada → Tokugawa Ieyasu
Father: Yonekitsu Katsunobu
Siblings: Tsuneharu, Masanobu
Children: Masakatsu, Haruchika
Yonekitsu Masakatsu served as a bushō and hatamoto from the Sengoku to early Edo periods.
Masakatsu was born as the son of Yonekitsu Tsuneharu.
In 1600, Masakatsu participated in the Conquest of Aizu. Later that year, he was appointed to serve as the magistrate for Sakai. From 1603 to 1604, he conducted land surveys in Mikawa Province. In 1611, Masakatsu, together with Itakura Katsushige, conducted surveys in Yamashiro Province.
In 1613, in the village of Akutagawa in the Shimakami District of Settsu Province, the villagers made a claim against him for failing to arrest a murderer as repayment for a bribe accepted by a subordinate so, on 5/2, he was removed from his position as a magistrate and exiled to Awa Province in Shikoku.
On 2/22 of Keichō 19 (1614), Masakatsu was sentenced to death by beheading. At this time, his younger brother, Haruchika, was stripped of his status as a bushi. Masakatsu had a close relationship with Ōkubo Nagayasu so it is surmised that he was punished for complicity in an event known as the Ōkubo Nagayasu Incident.