Born at Isaku Castle in Satsuma (Kagoshima) as the eldest son of Shimazu Takahisa; his younger brothers were Yoshihiro, Toshihisa and Iehisa. His grandfather Jisshinsai (Tadayoshi), looking at the four brothers, is said to have praised Yoshihisa as having the makings of supreme commander of the three provinces.
He fought in battle for the first time at Iwatsurugi Castle in Ōsumi, together with his brothers Yoshihiro and Toshihisa. At this time the Shimazu, under his father Takahisa, were fighting the surrounding local lords in an effort to unite the three provinces of Satsuma, Ōsumi and Hyūga.
His father Takahisa handed him the headship and he became lord of the Shimazu. Yoshihisa set the overall course himself and entrusted each front to his brothers: the fierce Yoshihiro, the shrewd Toshihisa and the tactician Iehisa. The brothers' firm unity became the great strength of the Shimazu.
The Itō of Hyūga attacked with a large army, but his brother Yoshihiro defeated them with far fewer men (Battle of Kizakibaru). This victory greatly weakened the Itō and opened the way for the Shimazu to extend their power into Hyūga.
He drove Itō Yoshisuke out of Hyūga and at last united the three provinces of Satsuma, Ōsumi and Hyūga, fulfilling the long-held wish of his grandfather's and father's generations. The expelled Itō turned to Ōtomo Sōrin of Bungo, which led to a great war with the Ōtomo.
He crushed the large army of Ōtomo Sōrin, which had invaded Hyūga, at the Battle of Mimikawa. The Ōtomo lost many senior vassals and their power declined, greatly changing the balance of power in Kyūshū. The Shimazu went on to extend their power from the south of Kyūshū toward the north.
When Ryūzōji Takanobu of Hizen attacked the Arima of Shimabara, Yoshihisa sent his brother Iehisa to help the Arima, and they defeated the Ryūzōji army at the Battle of Okitanawate. Takanobu lost his life in this battle, and the Shimazu came within reach of almost all of Kyūshū.
Because he ignored Toyotomi Hideyoshi's order to stop fighting and kept attacking the Ōtomo, he faced Hideyoshi's huge Kyūshū campaign. Cornered, Yoshihisa shaved his head, took the name Ryūhaku, and surrendered to Hideyoshi at Taihei-ji in Sendai. He was allowed to keep Satsuma, Ōsumi and other lands.
In Hideyoshi's invasion of Korea his brother Yoshihiro crossed the sea. At home, the retainer Umekita Kunikane, unhappy with the campaign, rose in revolt (the Umekita Uprising), and his brother Toshihisa, held responsible, lost his life. Yoshihisa had no choice but to obey Hideyoshi and is said to have grieved deeply.
At the Battle of Sekigahara, Yoshihiro fought for the Western Army with only a few men and broke through the enemy to return home. Yoshihisa strengthened the defense of the home provinces and after the battle negotiated patiently with Tokugawa Ieyasu, refusing to rush to the capital region and putting the survival of the house first.
After long negotiations, Ieyasu confirmed the Shimazu lands as they were, and Yoshihiro's son Tadatsune (later Iehisa) became head of the house. While many daimyō who had sided with the Western Army had their lands cut or confiscated, the Shimazu came through with almost no loss of territory.
He died at his castle in Kokubu, Ōsumi (now Kirishima). Even in his last years he watched over the domain's affairs from Kokubu, working with his brother and nephew to protect the Shimazu house. He is remembered as the lord who came close to uniting Kyūshū and who, even after defeat, kept his house and lands intact.
Ryuzoji TakanobuŌtomo SōrinToyotomi HideyoshiTokugawa IeyasuToyotomi Hidenaga
Kikkawa MotoharuLuís FróisKobayakawa TakakageAsakura YoshikageŌmura SumitadaOda NobunagaHosokawa Yūsai (Fujitaka)Shimazu Yoshihiro
People of the Sengoku/Azuchi-Momoyama period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.