During the reconstruction the ternary phase diagram of glycerol monooleate (GMO)/ethanol/water, we detected a novel structure not previously seen. The new phase, denoted Q_L (micellar cubic liquid), is located within the 49–54 wt.-% water/41–33 wt.-% GMO binary mixture line and at 10–13 wt.-% EtOH in a small island within the phase diagram close to the cubic liquid-crystalline phase region. The Q_L phase is transparent (not tinted), of a low viscosity (36.6 Pa s), non-birefringent, and stable at room temperature. Evidence from severe centrifugation, synchrotron small-angle X-ray scattering (SAXS) measurements, and rheological behavior revealed that the sample is a single phase. SAXS reflections suggest that two types of domain may coexist. The symmetry of the Q_L phase is Pm3n. A cubic micellar structure is the dominant mesostructure of this unique sample. Cryo-TEM images show highly ordered domains with cubic symmetry, of lattice parameter 103 ± 2 Å. A possible transformation pathway to the Q_L phase is a ‘rupture and refusion’ mechanism, as the phase seems to have discontinuous symmetry.