The laser-flash photolysis technique combined with resonance fluorescence detection of OH was used to investigate the kinetics of the title reaction at temperatures between 246 and 353 K and at a total pressure of 75 +/- 1 Torr Ar. Under these conditions the rate coefficient shows a negative temperature dependence which is described by k(4)(246-353 K) = 7.0(-0.4)(+1.9) x 10(-11)(T/298)(-1.5+/-0.5) cm(3) s(-1). Both the large rate coefficient and trends in the reactivity of OH with HCl, HBr, and HI are suggestive of a reaction mechanism that proceeds without a significant activation barrier. The room temperature (294 K) rate constant is k(4) = 6.5(-0.4)(+2) x 10(-11) cm(3) s(-1), which is significantly larger than previous measurements. Reasons for this difference and the implications of the new rate coefficients for the lifetime of HI in the atmosphere are discussed.