Single-crystal Fe nanowires (NWs) were synthesized on SiO 2 /Si substrates by chemical vapor deposition (CVD) using a two-flow system in the presence of FeO nanoparticles as catalysts. Transmission electron microscopy observations and an electron diffraction analysis revealed that the NW was defect-free α-Fe (bcc structure) oriented in the ⟨100⟩ direction. A plausible mechanism of the Fe NW growth is suggested based on the observations of the morphology and characteristic diameter of the Fe NW. We found that the NWs became polycrystalline when their diameter was approximately 100 nm. The excellent crystal quality of the single-crystal NW was confirmed by electron diffraction and the residual resistance ratio. Magnetic uniformity and a strong shape-anisotropic behavior of magnetization were observed by measuring the hysteresis loop and the angle dependence of the magneto-optical Kerr effect, respectively.