Neutrophilic, microaerophilic iron(Ⅱ)-oxidizing bacteria (FeOB) can oxidize iron(Ⅱ) for energy via O₂-dependent mechanisms under suboxic, slightly-acidic to circumneutral conditions. This biological oxidation process commonly produces copious amorphous iron(Ⅲ) oxyhydroxides, a preferential substrate for dissimilatory iron(Ⅲ) reduction (iron respiration). Such oxyhydroxides have the potential to accelerate iron geochemical cycling at redox interfaces in terrestrial and aquatic systems. Despite reports on neutrophilic, microaerophilic FeOB since the 1830s, associated research progress has been slow, largely due to difficulty in laboratory cultivation and isolation of these organisms. Until the mid-1990s, modified FeS gradient methods were used for isolation of novel obligate FeOB from diverse habitats and substantial progress was achieved in understanding bacterial iron(Ⅱ) oxidation. Representative neutrophilic, microaerophilic FeOB include stalked Gallionella and Mariprofundus, sheathed Leptothrix and Sphaerotilus, and several non-stalk-forming, unicellular species such as Sideroxidans, Ferritrophicum and Ferrocurvibacter. Related species have frequently been found in redox transition zones of circumneutral-pH, iron-rich environments such as groundwater seeps, wetland rhizosphere soils and deep-sea hydrothermal vents. Bacterial iron(Ⅱ) oxidation is of global significance to biogeochemical iron cycling and other elements such as C, N, P, S and Mn. Bacterially-mediated iron cycling also influences the fate and transport of organic compounds and several trace metals. There is growing interest in understanding the role of neutrophilic, microaerophilic FeOB in biomineralization, geologic evolution, global climate change, and other fundamental geochemical processes. Here we review recent findings regarding bacterial iron(Ⅱ) oxidation under suboxic, circumneutral-pH conditions, and summarize associated methodologies for studying the ecology of neutrophilic, microaerophilic FeOB. Recommendations are provided regarding future study of these organisms and associated biogeochemical processes.