Dynamics of water in Nafion 117 membranes, in the acid form, at two hydration levels and several temperatures were investigated by means of dielectric relaxation spectroscopy in both, low (10−2 to 107 Hz, 25 to −80 °C) and microwave (0.045-26 GHz, 35 °C) frequency regions by employing different experimental setups. Three states of water were identified: a) strongly bound to the sulfonic groups (in agreement with other investigations) forming the first hydration layer; b) loosely bound, surrounding the first layer and c) free water, having similar dynamics as in the bulk state.