Ishibutai kofun is a stone kofun or tumulus of the Asuka period in the east of Shimanoshō, Asuka, Nara Prefecture, Japan. The kofun is believed to be the tomb of Soga no Umako. It occupies an area of 27 m², and is the largest known megalithic structure in Japan. The kofun is also known as the Ishibutoya Kofun.