Corals associate not only with dinoflagellates, which are their algal endosymbionts and which have been extensively studied over the past four decades, but also with a variety of other microorganisms. The coral microbiome includes dinoflagellates, viruses, fungi, archaea and bacteria, with knowledge of the latter growing rapidly. This Review focuses on the bacterial members of the coral microbiome and draws parallels with better-studied microbiomes in other biological systems. We synthesize current understanding of spatial, temporal and host-specific patterns in coral-associated bacterial communities, the drivers shaping these patterns, and the role of the microbiome in acclimatization and adaptation of the host to climate warming. We discuss how this knowledge can be harnessed to assist the future persistence of coral reefs and provide novel perspectives for the development of microbiome engineering and its implications for coral reef conservation and restoration.