We report the first direct kinetic study of the gas-phase reaction NaOH + H -> Na + H2O, which is central to the chemistry of sodium in the upper atmosphere and in flames. The reaction was studied in a fast flow tube, where NaOH was observed by multiphoton ionization and tithe-off-light mass spectrometry, yielding k(NaOH + H, 230-298 K) = (3.8 +/- 0.8) X 10(-11) cm(3) molecule(-1) s(-1) (at 2 sigma confidence level), showing no significant temperature dependence over the indicated temperature range and essentially in agreement with previous estimates of the rate constant in hydrogen-rich flames. We show, using theoretical trajectory calculations, that the unexpectedly slow, yet T-independent, rate coefficient for NaOH + H is explained by severe constraints in the angle of attack that H can make on NaOH to produce H2O. This reaction is also central to explaining Na-catalyzed flame inhibition, which has been proposed to occur via the sequence Na + OH (+ M) -> NaOH followed by NaOH -> H Na + H2O; thereby effectively recombinating H and OH to H2O. RRKM calculations for the recombination of Na and OH yield k(Na + OH + N-2, 300-2400 K) = 2.7 X 10(-29) (300/T)(1.2) cm(6) mblecule(-2) s(-1), in agreement with a previous flash photolysis measurement at 653 K and Na-seeded flame studies in the 1800-2200 K range. These results therefore provide strong evidence to support the mechanistn of flame inhibition by Na.