The oxygen redox reaction (ORR) in pyrrolidinium-based ionic liquids (ILs) without and with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is investigated at different temperatures for lithium/oxygen battery application. Results obtained by cyclic voltammetry, rotating disk electrode, and ultramicroelectrode potential steps at glassy carbon are reported and discussed in relation to the physical–chemical properties of the investigated ILs. Diffusion coefficients and solubility of oxygen in the ILs and tentative values of ORR heterogeneous rate constant in ILs without LiTFSI are reported. The effect of lithium salt on the ORR in IL is also discussed in view of lithium/oxygen battery application.