An evaluation of the virus population in rice plants using next-generation sequencing technologies resulted in the discovery of a new RNA virus, tentatively named rice virus A (RVA). The complete RVA genome sequence was determined and analyzed, revealing a genome organization resembling that of viruses classified in the genera Aureusvirus, Tombusvirus and Zeavirus within the family Tombusviridae. With 4,832 nucleotides, the RVA genome may be the largest monopartite genome sequenced to date in the family Tombusviridae. The 453-amino acid RVA coat protein shares the highest identity with the gp3 protein of an unclassified carascovirus, SF1 (GenBank accession no. KF510027) isolated from San Francisco wastewater, rather than the coat protein of any known member of the family Tombusviridae. These novel characteristics represent a significant divergence from the genomes of viruses belonging to the sixteen existing genera of the family Tombusviridae, demonstrating that RVA is likely a new family member.