Born at Himeji in Harima (Hyōgo), the eldest son of Kuroda Yoshitaka (Kanbei). His childhood name was Shōjumaru. His father Kanbei would later become famous as Toyotomi Hideyoshi's strategist.
As a pledge of his father's service to Oda Nobunaga, he was sent as a hostage and raised at Nagahama in Ōmi (Shiga), Hideyoshi's castle town. Hideyoshi's wife Nene is said to have been fond of him.
His father Kanbei went to Arioka Castle to persuade Araki Murashige, who had rebelled against Nobunaga, and was taken prisoner. Suspecting that Kanbei, who did not return, had betrayed him, Nobunaga ordered Shōjumaru killed, but Takenaka Shigeharu (Hanbei) secretly hid the boy and saved his life.
He joined Hideyoshi's Kyushu campaign with his father and won distinction. His father received lands at Nakatsu in Buzen (eastern Fukuoka and northern Ōita), and Nagamasa worked hard to put down uprisings there and build up the castle town.
His father retired, and Nagamasa succeeded as lord of Nakatsu Castle. Besides the wit he inherited from his father, he became known as a warrior of great courage in battle.
In Hideyoshi's invasions of Korea he crossed to the peninsula leading an army in the Bunroku campaign. He went again in the Keichō campaign and fought in many battles under hard conditions. From this time his rivalry with Ishida Mitsunari and others deepened.
At the Battle of Sekigahara he joined Tokugawa Ieyasu's Eastern Army. He not only fought hard on the field but also won over Kobayakawa Hideaki, Kikkawa Hiroie and others to weaken the Western Army, greatly helping the Eastern Army win. For this he was given Chikuzen (Fukuoka), worth over 520,000 koku.
He began building a new castle near Hakata and named it Fukuoka after Fukuoka in Bizen (Okayama), linked with the Kuroda family. The castle and town took about seven years to complete and, together with the merchant city of Hakata, became the basis of today's Fukuoka City.
His father Kanbei (Josui) died. Nagamasa treasured his father's teachings and later left written guidance for his descendants and retainers on how to preserve the house.
In the Winter Siege of Osaka he was ordered to stay behind in Edo, but he fought on the Tokugawa side in the Summer Siege of Osaka. The Osaka Summer Siege Screen, which he is said to have commissioned, is famous for showing even the ordinary people caught up and fleeing in the fighting.
He went to Kyoto in the shogun's train and died of illness at Hōon-ji there. Just before his death he left a testament for his retainers, and Fukuoka domain was passed down in the Kuroda family until the Meiji era.
Oda NobunagaToyotomi HideyoshiTokugawa IeyasuTakenaka Shigeharu (Hanbei)Kuroda Yoshitaka (Kanbei)Ishida MitsunariKobayakawa HideakiHachisuka Masakatsu
Ōtani YoshitsuguDate MasamuneSanada Yukimura (Nobushige)Tachibana MuneshigeYodo-donoItō MancioHasekura TsunenagaUkita Hideie
People of the Sengoku/Azuchi-Momoyama period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.