Hatakeyama Naomasa served as a bushō during the Sengoku period. He was the seventh head of the Hatakeyama-Sōshū family. His common name was Jirō.
Around 1460, a succession dispute for control of the Hatakeyama clan erupted between Hatakeyama Yoshinari and his cousin, Hatakeyama Masanaga, becoming one of the triggers for the Ōnin-Bunmei War enveloping Kyōto and its environs from 1467 to 1477. The succession dispute resulted in a division of the clan into the Hatakeyama-Sōshū family and the Hatakeyama-Bishū family. Yoshinari was the first head of the Hatakeyama-Sōshū family, wielding influence primarily in Kawachi and Yamato provinces.
In 1531, Naomasa was born as the eldest son of Hatakeyama Ariuji – a shugo daimyō and the sixth head of the Hatakeyama-Sōshū family.
On 5/9 of Tenbun 18 (1549), Nasamasa’s father, Ariuji, allied with the supporters of Hosokawa Harumoto in a battle in Kitasho in Sakai in Izumi Province against the forces of Miyoshi Nagayoshi and Yusa Naganori backing Hosokawa Ujitsuna. Those fighting for Harumoto, however, were defeated. On 6/24, at the Battle of Eguchi, Harumoto lost and his administration crumbled. This led to the downfall of the Hatakeyama-Sōshū family, but, in the midst of these development, on 6/4, a sealed document was issued that provided an exemption from the payment of taxes to the Kanshin Temple, suggesting that Naomasa succeeded to the headship of the clan around this time.
In 1552, Naomasa exercised power in the Uchi District of Yamato Province, and, together with retainers including Hira Zaemon Taifu Masasuke and Yusa Etchū-no-kami Iemori, attempted to initiate a battle to regain control of Kawachi Province. At this time, the Hatakeyama-Bishū family governing Kawachi was beset by internal unrest, including the assassination of a senior retainer named Yusa Naganori and the purge of members of the family from Kayafuri. It appears that Naomasa sought to take advantage of their vulnerability, but, owing to their alliance with Miyoshi Nagayoshi, despite their immediate challenges, the Hatakeyama-Bishū maintained a strong foundation so Naomasa’s plan failed to bear fruit.
Thereafter, in 1556, Yasumi Munefusa, a member of a council of senior retainers referred to as the uchishu, or inside group, under Hatakeyama Takamasa of the Hatakeyama-Bishū family, attack the Fuse clan of Yamato. Naomasa joined forces with the Fuse clan, but, around this time, the influence of the Hatakeyama-Sōshū family in the border area between Yamato, Kawachi, and Kii provinces was in decline. In the fifth month of 1565, after the killing of Ashikaga Yoshiteru (the thirteenth shōgun) by the Miyoshi clan in an event known as the Eiroku Incident, on 8/26, Naomasa responded to a request from Yoshiteru’s younger brother, Kakukei (later known as Ashikaga Yoshiaki) who, at the time, was a monk at the Ichijō monastery of the Kōfuku Temple in Nara. However, Naomasa’s whereabouts after this event are unknown.
Under one theory, through the offices of Matsunaga Hisahide, he became a retainer of Hatakeyama Takamasa and his descendants served Toyotomi Hideyori.
According to the Shinchō-kōki, the authenticated biography of Oda Nobunaga, the wife of Bessho Yoshichika was a daughter of the Hatakeyama-Sōshū family. She may have been the daughter of Naomasa’s father, Ariuji.