Origins and early career
Kiyomasa was born in what is now Nakamura-ku, Nagoya to Katô Kiyotada. Kiyotada's wife, Ito, was a cousin of Toyotomi Hideyoshi's mother. Kiyotada died while his son (then known as Toranosuke) was still young. Soon after, Toranosuke entered with Hideyoshi, and in 1576, at age 15, was granted a reward of 170 koku (rice). He fought in Hideyoshi's army at the Battle of Yamazaki, and later, at the Battle of Shizugatake. Owing to his achievement in that battle, he became known as one of the Seven Spears of Shizugatake. Hideyoshi rewarded Kiyomasa with a reward of 3,000 koku.
When Hideyoshi became the kampaku in the summer of 1585, Kiyomasa received the court title of Kazue-no Kami and junior 5th court rank, lower grade (ju goi-no ge). In 1586, after Higo Province was confiscated from Sassa Narimasa, he was granted 250,000 koku of land in Higo (roughly half of the province), and given Kumamoto Castle as his provincial residence.