Ijuin Tada'aki(伊集院忠朗; 1520–1561) was a retainer of the Japanese Shimazu clan during the Sengoku period of Japan.
[1] Under Tada'aki, the Ijuin clan rose to prominence as one of the most important vassals of the Shimazu clan.
Tada'aki had his troops use matchlock guns at the Siege of Kajiki in 1549.
For these and other contributions and services, he held the post of the top karō until 1556 and governed as the top official of the clan.
While having a party with Kimotsuki Kanetsugu in 1561, Tada'aki offended Kanetsugu so badly that the humiliated Kanetsugu started a war that the Shimazu clan wanted all along.