Ruyangosaurus (Ruyang County lizard) is a genus of titanosauriform sauropod dinosaur recovered from the Early Cretaceous Haoling Formation of China.

The type species is R. giganteus, described in 2009 by Lü Junchang et al.[1] Along with Huanghetitan and Daxiatitan, Ruyangosaurus is among the largest dinosaurs discovered in Cretaceous Asia.

In 2016 Gregory S. Paul gave a length of 30 meters (98 ft) and a weight of 50+ tonnes (55 short tons) - making it a 'mega-sauropod'.

[5] Comprehensive phylogenetic analyses of Titanosauriformes conducted by Philip Mannion and colleagues in 2013 found Ruyangosaurus to be in a polytomy with Andesaurus and other basal titanosaurs and near-titanosaur somphospondyls, supporting the original description's assertion of phylogenetic proximity of it and Andesaurus, though not the precise taxonomic assignment, with further modifications of the dataset resolving similar conclusions.

A phylogenetic dataset following the description of additional material for Ruyangosaurus to be a non-titanosauriform macronarian, closely related to Yunmenglong.