Nickel is increasingly used in both IC and photovoltaic device fabrication, yet it has the potential to create highly recombination-active precipitates in silicon. For nearly three decades, the accepted nickel diffusivity in silicon has been D N i (T) = 2.3 × 10 - 3 exp (- 0.47 eV / k B T) cm 2/s, a surprisingly low value given reports of rapid nickel diffusion in industrial applications. In this paper, we employ modern experimental methods to measure the higher nickel diffusivity D N i (T) = (1.69 ± 0.74) × 10 - 4 exp (- 0.15 ± 0.04 eV / k B T) cm2/s. The measured activation energy is close to that predicted by first-principles theory using the nudged-elastic-band method. Our measured diffusivity of nickel is higher than previously published values at temperatures below 1150°C, and orders of magnitude higher when extrapolated to room temperature.