Oyama Hidehiro served as the head of the Oyama clan during the Azuchi-Momoyama period.

Hidehiro was born as the illegitimate eldest son of Oyama Hidetsuna, a sengoku daimyō in Shimotsuke Province.

In 1590, as a result of the Conquest of Odawara by Toyotomi Hideyoshi, Hidetsuna and his sons lost their landholdings.  Thereafter, Hidehiro turned to his younger brother, Yūki Harutomo, for support.  Harutomo requested his adopted son, Yūki Hideyasu, to grant land to Hidehiro and promote him.  Around this time, Hidehiro inherited the headship of the clan from Hidetsuna because Hidetsuna’s lineal heir, Oyama Masatane, had earlier died of illness.  On 3/29 of an unknown year, Hidehiro died at the age of thirty-five.  This may have been around the time of the Battle of Sekigahara in the autumn of 1600, prior to the move by the Yūki clan to Echizen Province.  Hidetsuna did not follow the Yūki to Echizen, dying of illness shortly after their departure.