Hara Tanesada served as a bushō during the Sengoku period.  He was a retainer of the Chiba clan of Shimōsa Province and served as the head of the Shimōsa-Hara – the main branch of the Hara clan.

Tanesada was born as the son of Hara Tanekiyo, a bushō and retainer of the Chiba clan, the sengoku daimyō of Shimōsa.  Between 1528 and 1531, he built and served as the first lord of Konishi Castle in Ōami-Shirasato.  In 1539, after the retirement of Tanekiyo, Tanesada inherited the headship of the clan, becoming the lord of Oyumi Castle.  After the death of Usui Kagetane, his son-in-law and the head of the Usui clan, in 1557, he leveraged his relationship as a relative to enter Usui Castle as a guardian of Usui Hisatane, his grandson from a daughter married into the Usui.  Owing to good governance, he garnered the support of the retainers of the Usui and local citizenry, making Hisatane a puppet lord and becoming the de facto lord of Usui Castle.  Later, Hisatane was expelled and sought refuge with the Yūki clan.

In 1561, Masaki Nobushige, backed by the power of the Satomi clan of Kazusa Province, invaded and captured Usui and Oyumi castles in Shimōsa.  In 1564, at the Second Battle of Kōnodai, the Satomi clan suffered a major defeat to the Hōjō of Sagami Province whereupon, with the assistance of Chiba Tanetomi, Tanesada recaptured both castles.  Thereafter, Uesugi Kenshin mounted an attack against Usui Castle, but with the support of Shirai Taneharu, he repelled the Uesugi army.

Tanesada is deemed to have died in the fifth month of 1569, but in connection with the alliance between the Uesugi and the Hōjō in the autumn of that year, Uesugi Kenshin made references to the treatment of Tanesada, raising questions in regard to the timing of Tanesada’s demise.  In 1574, his lineal heir, Hara Tanehide, entered Usui Castle and, according to the genealogy of the Chiba clan, in 1575, Tanesada withdrew to Konishi Castle.  In any event, during the Genki era (1570 to 1573), Tanehide served as the head of the clan and, around 1569, there was a changing of the guard.