Morikawa Ujitoshi served as a bushō during the Sengoku and Azuchi-Momoyama periods.  His former surname was Horiba but he adopted the Morikawa surname from his mother’s side of the family.

Ujitoshi was born as the son of Horiba Ujikane, a bushi in Owari Province who served the Oda clan.  Ujikane died in 1561.  Ujitoshi’s uncle, Morikawa Ujitsugu, served as a guest commander of Inoo Tsuratatsu, a retainer of the Imagawa clan.  In 1565, Ujitsugu and Tsuratatsu were killed in action.  Tokugawa Ieyasu, who was colluding with Tsuratatsu, recognized the contributions of Ujitsugu so invited Ujitoshi (as a family member Ujitsugu), engaging Ujitoshi to serve as a retainer under the Morikawa surname.  Thereafter, Ujitoshi served in numerous major battles for the Tokugawa clan.

Ujitoshi served valorously at the Siege of Horikawa Castle in 1568 and the Battle of Anegawa in 1570.  In 1572, he served in the rear guard at the Battle of Mikatagahara.  In 1574, he clashed against the army of Yamagata Masakage, a senior retainer of the Takeda clan, outside of Hamamatsu Castle.  In 1575, he contributed at the Battle of Nagashino.  In 1584, at the Battle of Komaki-Nagakute, Ujitoshi defended Hira Castle in the former territory of his father in Owari.  In 1590, he participated in the Conquest of Odawara. 

In 1592, Ujitoshi was awarded a fief of 2,000 koku in the Hiki District of Musashi Province and the Yamabe District of Kazusa Province.

His first and second sons kept the family name while serving as direct retainers of the Edo bakufu.  His third son, Morikawa Shigetoshi, became a rōjū, or member of the shōgun’s council of elders, and the first lord of the Shimōsa-Oyumi domain.  Ujitoshi’s siblings and cousins all used the Morikawa surname.  His brother-in-laws – Mano Nobushige (the husband of his older sister) and Yamaha Nagakatsu (the husband of his younger sister) – died early so Ujitoshi raised their sons, Shigetsugu and Nagatsugu, both of whom adopted the Morikawa surname.