Rotaviruses C (RVCs) have been detected in pigs, humans, cows, ferrets and dogs. Despite their zoonotic impact and pathogenicity, the genetic characterization of RVCs is incomplete, unlike rotaviruses A (RVAs), whose genetics are well studied. Several studies reported partial and complete genomic sequences for multiple porcine and canine RVCs. We aimed to establish a complete genome-based genotyping system for RVCs, by analysing complete genome data from 22 porcine RVCs identified in Japan from 2002 to 2010, along with those from multiple human, bovine, porcine, canine and ferret RVCs reported in several previous studies. Comparative sequence analyses among RVCs from various host species demonstrated that porcine RVCs had a high level of genetic diversity. In addition, phylogenetic analyses of all 11 RNA segments indicated that porcine RVCs could be classified into multiple genotypes. Notably, the VP4 dendrogram divided bovine RVCs into multiple genotypes. Consequently, the provisional genotype classification for RVCs from terrestrial mammals revealed the existence of genotypes 18G, 21P, 13I, 4R, 6C, 6M, 9A, 8N, 6T, 5E and 4H for the genes VP7, VP4, VP6, VP1, VP2, VP3, NSP1, NSP2, NSP3, NSP4 and NSP5, respectively, based on the cut-off values as defined by the Rotavirus Classification Working Group. The system established in this study deepens our understanding of RVC evolution and facilitates the discovery of genetic events (gene reassortment and interspecies transmission) among RVCs.