The present work reports the discovery and the complete genome sequencing of a novel member of the genus Vitivirus in the family Betaflexiviridae (subfamily Trivirinae) from a symptomless grapevine of unknown variety from Portugal. Total RNAs extracted from phloem scrapings were sequenced using Illumina technology. Bioinformatic analysis of the RNA-seq data revealed a mixed infection involving three viruses and two viroids in addition to a novel vitivirus. Completion and analysis of the genome sequence (7446 nt excluding the polyA tail) showed a typical vitivirus genomic organization. Phylogenetic analysis of the various ORFs clearly showed the new virus to belong in the genus Vitivirus, but sequence divergence firmly establishes it as a member of a new species, for which the name "Grapevine virus H" is proposed.