An emerging challenge occurs for recovering ionic liquids (ILs) because of their exponential growth in academic and industrial applications. We report for the first time to reclaim water-soluble ILs from their aqueous solutions by osmotically driving water to spontaneously permeate through semi-permeable membranes. Theoretical simulation indicates a weak hydrability of ILs and a tendency to form micelles in water. We thus demonstrate a significant difference in osmotic pressures between the aqueous solutions of ILs and inorganic salts. Four categories of broadly representative ILs are continuously recovered from their diluent aqueous solutions (~1 wt%) with semi-permeable membranes. Eventually, a record-high concentration up to 58–78 wt% is achieved in this work. Our strategy integrates superiorities of low energy consumption, universal applicability toward ILs, diversified selection of semi-permeable membranes, almost unattenuated water flux and high rejection to ions, hopefully providing new insights into the authentic “green” industrial applications of ILs.