Abstract: A process for thermal management by feed gas conditioning in high temperature fuel cell systems wherein at least a portion of a fuel feed stream is chemically reacted in an exothermic chemical reaction in an external zone thermally separated from the fuel cell system and at least a portion of the products of such exothermic chemical reaction are passed to an internal zone in thermal exchange with the fuel cell system and reacted in an endothermic chemical reaction thereby absorbing heat from the exothermic electrochemical reaction within the fuel cell system producing a process stream of higher thermal energy. At least a portion of the higher thermal energy stream is removed from the fuel cell system, thereby maintaining the desired operating temperature in the fuel cell system. The process significantly reduces energy requirements of the system and significantly increases overall system efficiency and the output voltage of the system.