We report on the use of N-methylacetamide (NMA) as an electrolyte solvent in a rechargeable Li-O2 battery. Despite a relatively high acidity of the secondary amide N-H group, NMA shows unexpected stability toward superoxide. Quantum chemical calculations are used to rationalize this behavior. A Li-O2 cell using a novel NMA/LiNO3 electrolyte is shown to have good cycling performance with a consistent charging profile, Li2O2 formed during discharge, and O2 detected as the primary gaseous product during charge. Resistance of secondary amides to chemical degradation in the O2 electrode makes them attractive candidates as electrolyte solvents for rechargeable Li-O2 batteries.