Phages are important predators of bacteria—they shape the structure, function, and evolution of natural microbial communities. Although the majority of phage genetic diversity has been increasingly unveiled, fundamental features of how phage-bacteria interactions remain poorly understood. Here, we characterize 8 novel lytic phages and 2 lysogenic phages isolated or induced from the marine bacterium Alteromonas and establish their host range on a diversified panel of 175 Alteromonas from 18 species. TEM and genome sequencing show alterophages are diverse, both morphologically and genetically; we unveil a broad host range as a dominant trait of the isolated Alteromonas phages. Each phage detected in this study has a weak host specialism on species and strain, and therefore their potential to promote horizontal gene transfer in the environment; Our findings indicate there was no significant correlation between host range and phage morphology or life history strategy.