Cheonmachong, formerly Tomb No.155 in South Korea, is a tumulus located in Gyeongju, South Korea. The name "Cheonmachong" means Sky horse tomb. This tomb was built in the style of Silla. Excavation of the tomb began on April 16, 1973 and is believed to date probably from the fifth century but perhaps from the sixth century CE. The tomb was for an unknown king of the Silla Kingdom.
The tomb, in typical Silla style, is a wood-lined chamber running east to west and is covered in a mound of boulders and earth. This kind of tomb is said to follow the pattern of a Scytho-Iranian tomb in Pazyryk, Russia. The tomb is 47 metres in diameter, 157 metres in circumference, and 12.7 metres in height.
The chamber of the tomb contained a lacquered wooden coffin which had burial goods placed around it. A total of 11,500 artifacts were recovered from the tomb. The name of the tomb derives from a famous painting of a white horse which is depicted on a birch bark saddle flap, also referred to as a mud-guard. The horse, a Cheonma, has eight legs and is depicted with wings on its feet.