Also known as: Mariko-jou (鞠子城)

Kabasawa Castle is a mountain castle located in Echigo (now Niigata Prefecture) said to be the place where Uesugi Kagekatsu was born. Its inner citadel was built at the mountain summit at an elevation of 300 meters (~984 feet).

During the 14th century, the castle was the stronghold of a vassal of Nitta Yoshisada. Nagao Kagetora (Uesugi Kenshin) became master of the castle during the Sengoku Period and commanded his brother-in-law Nagao Masakage to make alterations to it.

Since Kabasawa Castle lay on the three-province highway that was the shortest distance between Echigo and the Kantou, it was used as a communications base during Kenshin's Kantou expeditions. Masakage and his wife Sentouin seemed to have lived in the castle as well, and their son (later Uesugi Kagekatsu) was born there in the fifth year of their marriage.

After Kenshin's death, Houjou Ujiteru and Houjou Ujikuni dispatched by Houjou Ujimasa to aid their brother Uesugi Kagetora in the Otate no Ran crossed Mikuni Pass and captured Kabasawa Castle. The Houjou army made Kabasawa their base from which to attack Sakato Castle, but withdrew with the advent of winter.

Kagekatsu took the castle upon his victory in the Otate no Ran. He later abandoned the castle upon receiving the 120,0000-koku territory of the Aizu from Toyotomi Hideyoshi.