Weyl semimetals are characterized by their bulk Weyl points—conical band touching points that carry a topological monopole charge—and Fermi arc states that span between the Weyl points on the surface of the material. Recently, significant progress has been made toward the understanding and measurement of the physical properties of Weyl semimetals. Yet, potential applications remain relatively sparse. Here we propose Weyl semimetal nanowires as field-effect transistors, dubbed WEYLFETs. Specifically, applying gradient gate voltage along the nanowire, an electric field is generated, which effectively tilts the open surfaces, thus, varying the relative orientation between Fermi arcs on different surfaces. As a result, perfect negative refraction between adjacent surfaces can occur and longitudinal conductance along the wire is suppressed. The WEYLFET offers a high on/off ratio with low power consumption. Adverse effects due to dispersive Fermi arcs and surface disorder are studied.