A humidifier for humidification of a reactant gas in a fuel cell includes a container having a water-gas void volume disposed about a hollow core member, and a water-gas inlet and a gas outlet disposed on an outer surface of the container. At least a portion of the hollow core member is gas permeable and in fluid communication with the water-gas void volume. The hollow core member is further fitted with a reactant gas inlet and a reactant gas outlet for passage of the reactant gas through the hollow core member. The reactant gas outlet is equipped to be in fluid communication with the fuel cell to deliver a humidified reactant gas to the fuel cell. The humidifier is integrated within a fuel cell system. A method of humidifying a reactant gas in such a fuel cell system includes providing the humidifier and passing a reactant gas through it.