Okuyama Moriaki served as a bushō and daimyō during the Sengoku and Azuchi-Momoyama periods.

Moriaki was born as the son of Sakuma Morishige (Daigaku-no-jō).  Although a member of the Sakuma clan, Moriaki adopted the Okuyama surname based on the name of the Okuyama manor in Echigo Province where his ancestors resided.

In 1560, Moriaki made contributions at the Battle of Okehazama during which Imagawa Yoshimoto was killed in a surprise attack led by Oda Nobunaga.  Moriaki served Niwa Nagahide but, in 1585, when Niwa Nagashige moved to another province, Moriaki was engaged to serve under the direct command of Toyotomi Hideyoshi and granted a fief of 11,000 koku in Echizen Province.  Thereafter, he served for Hideyoshi in the Pacification of Kyūshū and the Conquest of Odawara.

After the Conquest of Odawara, Sakuma Yasumasa and Sakuma Katsuyuki (siblings) who had served the Hōjō clan went into hiding in the countryside.  Upon orders of Hideyoshi, Moriaki persuaded the siblings to serve the Toyotomi.  This arose from existing relationships including that Moriaki’s sister was the wife of Sakuma Morimasa (the older brother of Yasumasa and Katsuyuki) and Moriaki’s father, Morishige, was the older cousin of Sakuma Moritsugu (the father of Yasumasa and Katsuyuki).

After serving in the Bunroku Campaign, Moriaki died and his landholdings inherited by his second son, Okuyama Masayuki.  His eldest son, Okuyama Shigenari, served as a hatamoto, or direct retainer of the Edo bakufu, for a stipend of 1,000 koku.