Okudaira Tadamasa served as a bushō and daimyō during the early Edo period.  Tadamasa was the second lord of the Kōzuke-Yoshii domain and, later, the second lord of the Mino-Kanō domain.

In 1580, Tadamasa was born as the third son of Okudaira Nobumasa, the first lord of the Kanō domain.  His mother was Kamehime, the eldest daughter of Tokugawa Ieyasu.  He wed the daughter of Satomi Yoshiyori, Yōshunin-den.  Tadamasa was adopted by Tokugawa Ieyasu (his maternal grandfather) and permitted to use the Matsudaira surname so he was also called Matsudaira Tadamasa.

Born in Mikawa Province, in 1597, Tadamasa was adopted by Suganuma Sadatoshi and adopted the name of Suganuma Tadamasa.  After the death of Sadatoshi in 1602, he was released from his relationship through adoption and, following the retirement of his father that same year, succeeded him as the second lord of the Mino-Kanō domain.  Tadamasa, however, was frail of health, so his father continued to hold the real power and lead the affairs of the domain.

On 10/1 of Keichō 19 (1614), just before he was ordered to deploy for the Siege of Ōsaka, he suddenly complained of stomach pains and, around 12:00 noon on the next day, he preceded his father in death.  Tadamasa was thirty-five years old.  He was succeeded by his young son, Okudaira Tadataka.  There is a memorial tower for Tadamasa at the Okuno Temple on Mount Kōya in the environs of Kyōto.  There were plans for several daimyō from Mino to lead members of the Kanō domain for the Siege of Ōsaka, but owing to the death of Tadamasa and depression suffered by his father (Nobumasa) and Tadamasa’s younger brother (Tadaakira from the Kameyama domain) led soldiers from the Kanō domain and daimyō from Mino to the Winter Campaign of the Siege of Ōsaka.