New electrolyte solutions for rechargeable magnesium metal batteries were studied. The electrolyte solution composed of triethylene glycol dimethyl ether (triglyme) and butyl methyl triglyme as solvents and magnesium(II) bis(trifluoromethanesulfonyl)amide as a magnesium salt. The reversible deposition and dissolution of magnesium metal was achieved in these electrolyte solutions at ambient temperature. The electrochemical stability of triglyme-based electrolyte solutions showed high stability toward oxidation.