This work shows that Ru nanoparticles supported on high surface area nano MgO is a highly active and selective catalyst for CO2 methanation, which is a promising method to store renewable energy and limit the emission of greenhouse gasses. We studied the effect of the Ru loading on MgO supports with different surface areas and compared the results to the corresponding Ni-based catalyst. Our results show that high surface area MgO containing 5 wt % Ru has the highest activity. This catalyst was stable for more than 50 h and resulted in 54 % conversion at 375 ◦C, which, under the given reaction conditions, corresponds to a site time yield of 520 molCH4 molRu− 1 h− 1. For comparison, the Ni-based catalyst only resulted in 45 % conversion at 450 ◦C with a low selectivity to CH4 (STY=263 molCH4 molNi − 1 h− 1). Furthermore, Ru on high surface area MgO catalyst was already active at low temperature of 250 ◦C due to chemisorption and activation of CO2 on the MgO support, which is promising for low-temperature CO2 methanation.