The silicon liquid self-diffusivity was determined by pulsed laser melting of 30Si ion implanted silicon-on-insulator thin films. Secondary ion mass spectrometry was employed to measure the 30Si+ concentration-depth profile before and after melting and solidification. Melt depth versus time and total melt duration were monitored by time-resolved lateral electrical conductance and optical reflectance measurements. One-dimensional diffusion simulations were utilized to match the final 30Si+ experimental concentration spatial profile given the initial concentration profile and the temporal melt-depth profile. The silicon liquid self-diffusivity at the melting point is (4.0±0.5)×10−4 cm2/s. Calculations of buoyancy and Marangoni convection indicate that convective contamination is unlikely.