Also known as: 太郎四郎, Mogami Yoshichika (最上義親)

Second son of Mogami Yoshiaki who served Tokugawa Ieyasu from the age of 12. He was originally named Mogami Yoshichika, but was given the name Iechika by Ieyasu. In 1595 he became the vassal of Ieyasu's son, Tokugawa Hidetada.

His elder brother, Mogami Yoshiyasu was killed by their father, so Iechika became the 12th head of the Mogami Clan in 1614 as well as the second-generation lord of Yamagata-han.

He died suddenly at Yamagata-jou at the age of 36. His eldest son Mogami Yoshitoshi succeeded him, but internal strife had already begun within the Mogami Clan before his death, and by judgement of the Shogunate the Mogami Clan's land and status were forfeited.