Ethylene glycol is currently produced via an energy-intensive two-step thermocatalytic process that results in substantial CO₂ emissions. Sustainable ethylene glycol production via ethylene electro-oxidation powered by renewable electricity is desirable; however, direct ethylene electro-oxidation suffers from unsatisfactory product selectivity, particularly at high production rates. Here we report a cascade strategy for efficient and selective production of pure ethylene glycol solution under ambient conditions with no detectable by-product formation. Specifically, ethylene is converted to ethylene glycol on a catalyst/solid-acid composite using electrochemically generated hydrogen peroxide as the oxidant. Using an integrated solid-electrolyte reactor, we achieved high electron utilization efficiency of 60–70% at industrially relevant current densities (100–500 mA cm⁻²) for ethylene glycol production with full product selectivity (~100%). We further integrated this system with a CO₂ electroreduction reactor and demonstrated the sustainable production of pure ethylene glycol using CO₂ and water as the only feedstocks.