We report on the development of nanowire-based field-effect transistors operating as high sensitivity terahertz (THz) detectors. By feeding the 1.5 THz radiation field of a quantum cascade laser (QCL) at the gate-source electrodes with a wide band dipole antenna, we record a photovoltage signal corresponding to responsivity values >10 V/W, with impressive noise equivalent power levels <6 x 10(-11) W/root Hz at room temperature and a wide modulation bandwidth. The potential scalability to even higher frequencies and the technological feasibility of realizing multi-pixel arrays coupled with QCL sources make the proposed technology highly competitive for a future generation of THz detection systems.