Abstract: Many organisms, including microbes, insects, fish, birds and mammals, sense and use Earth’s magnetic field for orientation and navigation, a physiological trait known as magnetoreception or magnetotaxis. Magnetotactic bacteria (MTB) biomineralize intracellular chain(s) of membrane-bounded, nano-sized magnetosome crystals of either magnetite (Fe3O4) or greigite (Fe3S4) for magnetotaxis. So far, magnetosomes in MTB are the only magnetoreceptor that have been characterized and are therefore the model system with which the origin and evolution of magnetotaxis as well as microbial biomineralization can be explored. MTB also play important roles in the geochemical cycling of iron, sulfur, nitrogen and carbon. Here we review recent contributions to the fields of diversity, biogeography, origin, magnetotaxis, biomineralization mechanisms and environmental function of MTB. Novel technologies including metagenomics, single-cell genomics and nanoscale secondary ion mass spectrometry (NanoSIMS) that have recently been successfully applied to the research of MTB are also~summarized.