Viral metagenomics uses metagenomic technologies to detect viral genomic material from diverse environmental and clinical samples.[1][2] Viruses are the most abundant biological entity and are extremely diverse; however, only a small fraction of viruses have been sequenced and only an even smaller fraction have been isolated and cultured.[1][3] Sequencing viruses can be challenging because viruses lack a universally conserved marker gene so gene-based approaches are limited.[3][4] Metagenomics can be used to study and analyze unculturable viruses and has been an important tool in understanding viral diversity and abundance and in the discovery of novel viruses.[1][5][6] For example, metagenomics methods have been used to describe viruses associated with cancerous tumors and in terrestrial ecosystems.[7]