Sassa Narimasa (佐々 成政, February 6, 1536 – July 7, 1588) was a Japanese samurai lord of the Sengoku through Azuchi–Momoyama periods. He entered Oda Nobunaga's service at the age of 14 and remained in his service throughout Nobunaga's rise to power. He was a member of the so-called Echizen Sanninshu (Echizen Triumvir) along with Maeda Toshiie and Fuwa Mitsuharu. He was also known as Kura-no-suke (内蔵助).
 Sassa Narimasa was born to Sassa Morimasa in what is now Nishi-ku, Nagoya (situated in contemporary Aichi District, Owari Province). He became a retainer of Oda Nobunaga in 1550. Narimasa was a military commander under Nobunaga, and the leader of Oda's Kurohoro-shū (黒母衣衆, lit. 'Black Mantle group'), a Military group with a black Horo (cloak) on their backs.
 In 1560, after his brothers were killed in battle, Narimasa took over the family estate and became the lord of the Hirajo Castle.
 Narimasa served Nobunaga throughout the latter's career. He was noted for his ability to lead matchlock forces, a position he regularly held.
 In 1567, he fought in the Siege of Inabayama Castle against Saito Tatsuoki from the Saitō clan.
 In 1570, Narimasa participated in the Siege of Kanegasaki, leading a few armed forces of horse guards, and worked to support Hashiba Hideyoshi using a firearms troop.
Later, he fought the Azai and Asakura clans in the  Battle of Anegawa, where he was in the rear guard.
 In 1575, Narimasa fought at the Battle of Nagashino against Takeda Katsuyori from Takeda clan. Later, he was given Komaru Castle in Echizen, where he had recently helped put down rioting Ikkō-ikki, and became a member of Echizen Sanninshu (Echizen Triumvir).
 In 1577, he participated in the Battle of Tedorigawa against Uesugi Kenshin from the Uesugi clan.
 In 1580, he was involved in stabilizing the Etchu Province, against an uprising of Ikko sect followers who supported Jimbo Nagazumi.
 In 1581, he defended Toyama Castle against Kawada Nagayori in the Battle of Arakawa.
 In 1582, he and Shibata Katsuie successfully laid siege to Uozu against Uesugi Kagekatsu from the Uesugi clan. He was granted Etchū Province as a reward for helping Shibata Katsuie fight the Uesugi clan. 
 In 1582, after Oda Nobunaga's death at Honnō-ji, at the Kiyosu meeting, Narimasa took the side of Shibata, but he could not participate in the battle of Shizugatake in 1583, since he could not leave Etchu where he was preparing for the attack of the Uesugi army at Matsukura Castle (Toyama Prefecture). After the death of Katsuie, Narimasa joined Tokugawa Ieyasu.
 In 1584, during the battle of Komaki Nagakute, he and the Tokugawa alliance unsuccessfully challenged the Toyotomi force under Maeda Toshiie at the Siege of Suemori.
 In 1585, he was defeated by Toyotomi Hideyoshi at Siege of Toyama, and later Narimasa submitted to Hideyoshi and his life was spared.
 In 1587, after the Hideyoshi Kyushu Campaign, he was given a fief in Higo Province in Kyushu. 
 In 1588, however, due to difficulties in suppressing a Higo Province local revolt, he committed suicide (seppuku) by Hideyoshi's instruction. The insurrection stemmed from survey of his province, which resulted in a change in the distance in which farmers transported their tax rice from 3 ri to 8 ri. 
 Later, after Higo Province was confiscated from Sassa Narimasa, land in Higo (roughly half of the province) and Kumamoto Castle granted to Kato Kiyomasa.
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