We have determined the lifetime of the OH-stretch vibration in pure liquid water as a function of temperature using femtosecond mid-infrared pump–probe spectroscopy. The lifetime T1 increases from 260±18 fs at T = 298 K to 320±18 fs at T = 358 K. The increase in lifetime with temperature can be quantitatively explained from the decrease in overlap resonance between the OH-stretch vibration and the overtone of the H–O–H bending mode.