SUMMARY: Metavir is a web server dedicated to the analysis of viral metagenomes (viromes). In addition to classical approaches for analyzing metagenomes (general sequence characteristics, taxonomic composition), new tools developed specifically for viral sequence analysis make it possible to: (i) explore viral diversity through automatically constructed phylogenies for selected marker genes, (ii) estimate gene richness through rarefaction curves and (iii) perform cross-comparison against other viromes using sequence similarities. Metavir is thus unique as a platform that allows a comprehensive virome analysis. AVAILABILITY: Metavir is freely available online at: http://metavir-meb.univ-bpclermont.fr. CONTACT: [email protected]. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.