Abstract: Magnesium and magnesium alloy foils have great potential for application in battery anodes, electromagnetic shielding, optics and acoustics, and biology because of their excellent specific damping, internal dissipation coefficients, magnetic and electrical conductivities, as well as high theoretical specific capacity. However, magnesium alloys exhibit poor deformation ability due to their hexagonal close-packed crystal structure. Preparing magnesium and magnesium alloy foils with thicknesses of less than 0.1 mm is difficult because of surface oxidation and grain growth at high temperatures or severe anisotropy after cold rolling that leads to cracks. Numerous methods have been applied to prepare magnesium alloy foils. They include warm rolling, cold rolling, accumulative roll bonding, electric plastic rolling, and on-line heating rolling. Defects of magnesium and magnesium alloy foils during preparation, such as edge cracks and breakage, are important factors for consideration. Herein, the current status of the research on magnesium and magnesium alloy foils is summarized from the aspects of foil preparation, defect control, performance characterization, and application prospects. The advantages and disadvantages of different preparation methods and defect (edge cracks and breakage) mechanisms in the preparation of foils are identified.