Siamotyrannus (meaning "Siamese Tyrant") is a genus of carnivorous theropod dinosaur from the early Cretaceous of Thailand. In 1993, Somchai Traimwichanon found a partial skeleton of a large theropod at the Phu Wiang 9 site in Khon Kaen. The holotype, PW9-1, was found in the Sao Khua Formation, dating from the Berriasian-Barremian. It includes the left half of the pelvis, five rear dorsal vertebrae, the sacrum with five sacrals, and thirteen front tail vertebrae. In 1998, a tibia and some individual teeth were referred to the species.