To realize renewable energy storage with a reduced carbon footprint for replacing fossil fuel and closing the unbalanced carbon cycle, electrochemical CO 2 splitting, commonly containing aqueous CO 2 reduction and water oxidation as core reactions, has received booming interest for its unique ability to produce chemicals and fuels from CO 2 powered by renewable electricity. In this Review, recent progress of electrochemical CO 2 splitting from a fundamental understanding to practical control of the main performance index, including production rate, product selectivity, and energetic efficiency, is discussed with the highlight of the methodologies used to increase CO 2 supply in water media and active site design. The roles of the main components in electrochemical CO 2 splitting devices, such as catalyst, electrode, electrolyzer, membrane, and electrolyte, are discussed. Finally, we also provide personal perspectives to highlight the opportunities to overcome low stability and limited selectivity for practical electrochemical CO 2 splitting.[a] Dr.