The Ichijo clan were a clan from Tosa Province in Shikoku, led by Fusamoto Ichijo. They had positions in the Imperial Court, but their power eventually waned and in 1545, their vassals, the Chosokabe, seized Kochi Castle and Fusamoto was killed leading resistance in other parts of Tosa Province.


The Ichijo clan were descended from the Fujiwara clan of northern Honshu, and were founded in 1246. The Ichijo held power in the Imperial Court, with some family members being kampaku (regent). The Ichijo clan had several branches, including one in Tosa Province, Shikoku, which was the main branch. Their power declined throughout the centuries, and in 1545, their popularity waned as well. Their powerful vassal Kunichika Chosokabe, assisted by his vassals, the Kira, rebelled against the Ichijo clan of Tosa. Kunichika took Kochi Castle from the Ichijo, founding the Chosokabe, but Fusamoto Ichijo led resistance outside of the castle after the downfall of the clan. Kunichika eventually pursued him, and was killed, but Fusamoto also died, bringing an end to the futile resistance offered by the last loyal Ichijo retainers.