Triggering oxidative steam reforming of ethanol was examined at low temperature over different supported Ni catalysts. Ni/Ce0.5Zr0.5O2, Ni/CeO2, and Ni/MgAl2O4 reduced at 800 degrees C enabled triggering the reaction at 100 degrees C without external energy input. This behavior was rationalized by internal heat supply by heat evolution from oxidation of Ce3+ and metallic Ni-0. The generated heat increased catalyst bed temperature up to autoignition temperature and thus the reaction was initiated. Especially, Ni/Ce0.5Zr0.5O2 triggered the reaction repeatedly without H-2 treatment from the second cycle. This is related to superior redox property and low autoignition temperature of ethanol oxidative steam reforming over Ni/Ce0.5Zr0.5O2 comparing with other supported Ni catalysts.