The authors report the use of a radio frequency silicon nanowire mechanical oscillator as a lowtemperature nuclear magnetic resonance force sensor to detect the statistical polarization of 1 H spins in polystyrene. In order to couple the 1 H spins to the nanowire oscillator, a magnetic resonance force detection protocol was developed which utilizes a nanoscale current-carrying wire to produce large timedependent magnetic field gradients as well as the rf magnetic field. Under operating conditions, the nanowire experienced negligible surface-induced dissipation and exhibited an ultralow force noise near the thermal limit of the oscillator.