Single-crystal MnWO4 nanowires were successfully prepared for the first time via a simple hydrothermal method without any surfactants. The as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). The effect of pH value, precursor, and reaction temperature on the formation of MnWO4 nanocrystals was investigated. The precursor was found to be vital to the formation of MnWO4 nanowires. It is rational to expect that one-dimensional nanostructures of other tungstates may also be synthesized by this simple method.