We have investigated electrical and magnetic properties of single-crystalline Fe5Si3 nanowires. The nanowire ensemble shows ferromagnetic properties with a high T-c of 380 K, small coercivity, and no remanence in zero field at room temperature. Such magnetic properties of the single-crystalline nanowires should give a chance to realize not only novel nanospintronic devices but also biomedical applications. Electrical transport measurements on single Fe5Si3 nanowire device show metallic properties with low resistivity of 487 mu . Omega . cm. Fe5Si3 nanowires are the first example of single-crystalline metallic ferromagnet with a T-c higher than room temperature.