Kōsa(光佐, February 20, 1543 – December 27, 1592), also known as Hongan-ji Kennyo (本願寺 顕如), was the 11th head of the Hongan-ji in Kyoto, and Chief Abbot of Ishiyama Hongan-ji, cathedral fortress of the Ikkō-ikki (Buddhist warrior monks and peasants who opposed samurai rule), during its siege at the end of the Sengoku period. He engineered many alliances, and organized the defenses of the cathedral to the point that most at the time considered Ishiyama Hongan-ji to be unbreachable.