- Death: 1599
- Title: Uemon daibu
- Other name: Ijuin Kôgan
- Distinction: Shimazu retainer
- Japanese: 伊集院忠棟 (Ijuuin Tadamune)
During Toyotomi Hideyoshi's invasion of Kyushu in 1587, Tadamune and Shimazu Iehisa were the first in Hyûga province to submit to Hideyoshi's authority. Tadamune ended up assisting in negotiations between Hideyoshi and the Shimazu. He impressed Hideyoshi and was granted territory of his own in Ôsumi. Already holding a position of privilege even among the Shimazu Elders, he was granted special position among Hideyoshi's vassals as well. Tadamune also developed a close relationship with Ishida Mitsunari. In 1595, he worked under Mitsunari in administering Hideyoshi's land survey within Shimazu territory. Once this was completed, Tadamune was transferred from Koyama to an 80,000 koku fief at Miyakonojô. He then led over 2,000 men in Hideyoshi's second invasion of Korea (1597-98). However, following Hideyoshi's death, he was summoned on 1599/4/4 to Shimazu Tadatsune's mansion, where he was murdered.