Ryōgūzan Kofun (両宮山古墳) is a Kofun period burial mound, located in the city of Awaiwa, Okayama Prefecture, in the San'in region of Japan. The tumulus was designated a National Historic Site of Japan in 1924 with the area under protection expanded in 1978 and again in 2006. It is largest keyhole-shaped burial mound in the Bizen region and the third largest in Okayama Prefecture, and the 39th largest in Japan.