Gamō Ujisato (蒲生 氏郷?, 1556 – March 17, 1595) was a Japanese daimyo of the Sengoku and Azuchi-Momoyama periods. The heir and son of Gamō Katahide, lord of Hino Castle in Ōmi Province, he later held Matsusaka (Ise Province) and finally Aizuwakamatsu Castle in Mutsu Province. He also controlled Obama Castle through one of his retainers, Gamō Chūzaemon.
Ujisato, known in his childhood as Tsuruchiyo (鶴千代?), was born in Hino, in the Gamō district of Ōmi Province in 1556. In 1568, Oda Nobunaga, who was en route to Kyoto, defeated the Rokkaku clan, who were the masters of Tsuruchiyo's father, Katahide (賢秀?). Upon the Rokkaku clan's defeat, Katahide as a former influential vassal, pledged loyalty to Nobunaga, and became an Oda retainer. However, the price of Katahide's pledge was giving up his son as a hostage, and so Tsuruchiyo was taken to Gifu, then the Oda clan's headquarters.