Kasugayama Castle (春日山城 Kasugayama-jō) was the primary fortress of the Japanese warlord Uesugi Kenshin during the Sengoku period. It is situated in what is now the city of Jōetsu, Niigata prefecture, and was originally built and ruled by the Nagao clan. It is listed on Japan's Top 100 Castles list due to its significance in culture, history and region.