Abstract The first archaeal virus was isolated over 40 years ago prior to the recognition of the three domain structure of life. In the ensuing years, our knowledge of Archaea and their viruses has increased, but they still remain the most mysterious of life׳s three domains. Currently, over 100 archaeal viruses have been discovered, but few have been described in biochemical or structural detail. However, those that have been characterized have revealed a new world of structural, biochemical and genetic diversity. Several model systems for studying archaeal virus–host interactions have been developed, revealing evolutionary linkages between viruses infecting the three domains of life, new viral lysis systems, and unusual features of host–virus interactions. It is likely that the study of archaeal viruses will continue to provide fertile ground for fundamental discoveries in virus diversity, structure and function.