AbstractBacteriophages (or phages) represent a persistent threat to the success and reliability of food fermentation processes. Recent reports of phages that infectStreptococcus thermophilushave highlighted the diversification of phages of this species. Phages ofS. thermophilustypically exhibit a narrow range, a feature that is suggestive of diverse receptor moieties being presented on the cell surface of the host. Cell wall polysaccharides, including rhamnose-glucose polysaccharides and exopolysaccharides have been implicated as being involved in the initial interactions with several phages of this species. Following internalization of the phage genome, the host presents several defences, including CRISPR-Cas and restriction and modification systems to limit phage proliferation. This review provides a current and holistic view of the interactions of phages and theirS. thermophilushost cells and how this has influenced the diversity and evolution of both entities.