Lifespan: Tenshō 9 (1581) to 8/6 of Genna 2 (1616)
Other Names: Sanjirō (childhood)
Title: Junior Fifth Rank (Lower), Governor of Nagato
Domain: Himeji (head of chief retainers)
Lord: Ikeda Terumasa → Ikeda Toshitaka → Ikeda Yukitaka
Father: Igi Tadatsugu
Mother: Seijuin (daughter of Hineno Takayoshi)
Siblings: Sister (wife of Ikeda Nagayoshi), sister (second wife of Ikeda Nagayoshi), Tadashige, Yukitake, Tadayuki
Wife: [Formal] Daughter of Moridera Tadakatsu, [Consort] from the Ushida clan
Children: Tsuruchiyo, Tadatoshi, Tadasada
Igi Tadashige served as a bushō during the Azuchi-Momoyama and early Edo periods. He was the head of the chief retainers of the Ikeda family of the Himeji domain in Harima Province. Tadashige was the second head of the Igi family.
Tadashige was born as the eldest son of Igi Tadatsugu, a chief retainer of the Ikeda family. He was born in Itami in Settsu Province. After his coming-of-age ceremony, he was granted a stipend of 1,000 koku. Following the Battle of Sekigahara, Ikeda Terumasa was transferred to Himeji Castle. Major reconstruction of Himeji Castle began in 1601, during which Tadashige served as a magistrate to manage the project. In 1603, Tadatsugu died so, at the age of twenty-three, he inherited the headship of the clan. Tadashige became the lord of Miki Castle with a fief of 33,000 koku and allocated 4,000 koku to his younger brother, Igi Yukitake. In 1604, Tadashige was invested with the titles of Junior Fifth Rank (Lower) and Governor of Nagato.
In 1613, Tadashige wed as his formal wife the daughter of Moridera Tadakatsu, a chief retainer of the Ikeda family.
On 8/6 of Genna 2 (1616), Tadashige died at the age of thirty-six. Igi Masaharu (Tadashige’s cousin and a chief retainer of the Igi family) managed the family while having Tadashige’s third son, Sanjūrō (later known as Igi Tadasada), at the age of five, inherit the headship of the clan.
Tadashige had three sons. The first and third sons were with his formal wife. The first son, Tsuruchiyo, died early. The third son was Sanjūrō. The second, Tadatoshi, born to a consort, became a retainer of the Ikeda family and was granted a stipend of 1,000 koku.