Karatsu Domain (唐津 土間員), located in Hizen Province, was a prominent feudal domain that held authority over the region. The ruling family's residence, known as Karatsu Castle, was situated in Karatsu City, Saga Prefecture. As the seat of power, Karatsu Castle served as a symbol of the domain's influence and played a crucial role in governing the surrounding territories. The domain's rule over Karatsu and its strategic location in Hizen Province contributed to its significance in the feudal era.^[1][2][3]

Terazawa Hirotaka was a loyal servant of Toyotomi Hideyoshi and played a significant role during the Bunroku War in 1592. Specifically, he worked as a construction worker for Hizen Nagoya Castle and was responsible for managing logistics. In recognition of his contributions, Hideyoshi granted him a commission that included Nagoya in 1593. Additionally, Hirotaka was appointed as the Nagasaki Magistrate and given control over approximately 83,000 koku in the entire Matsuura District. He further showcased his capabilities during the Keicho era by actively participating in Korea. Hirotaka's allegiance to the eastern army in the Battle of Sekigahara in 1600 led to remarkable achievements, resulting in him being rewarded with an additional 40,000 koku in the Amakusa District, Higo Province. This elevated his status to that of a feudal lord with a fief of 123,000 koku, marking the pinnacle of his success. However, following Hirotaka's death, his successor Terazawa Katataka faced challenges during the Shimabara Rebellion. The rebellion spread to Amakusa, and although Katataka was not as strict as Matsukura Katsuie, he implemented harsh policies within his fiefdom. Consequently, the shogunate held him responsible for the rebellion and confiscated his 40,000 koku in Amakusa. Overwhelmed by the stress, Katataka committed suicide. As he had no heir, the Terazawa clan faced a decline in their fortunes.

Several families were rotated through Karatsu for the next century: two generations of the Ōkubo clan; three generations of the Ogyū-Matsudaira clan, four generations of the Doi clan, and four of the Mizuno clan, including the famous reformer Mizuno Tadakuni. The domain then passed into the hands of Ogasawara Nagamasa,^[4] whose family remained until Karatsu domain was abolished in 1871. During the Boshin War of the Meiji Restoration of 1868-69, Ogasawara Nagamichi, the de facto ruler of Karatsu, led a group of his retainers on the side of the Ōuetsu Reppan Dōmei; after the fall of this alliance he went to Ezo and fought under the forces of the Ezo Republic. At the same time, Karatsu's domain-based administration was forced to pledge military support to the Satchō Alliance of Emperor Meiji.

Ogasawara Naganari, the Meiji period Imperial Japanese Navy admiral, was a descendant of the Ogasawara branch which ruled Karatsu.

• List of Han
• Abolition of the han system