Europium doped Y2O3spherical nanoparticles with the diameter ~10 nmobtained via cw laser vaporization are shown to crystallize in monoclinic symmetry class (C2/m space group). The size of nanoparticles established via HRTEM coincides with coherent scattering region established by XRD. Luminescence spectrum in the vicinity of ultranarrow transition demonstrates three peaks consistent with three inequivalent positions of Eu3+ ion in monoclinic Y2O3 lattice. Hypersensitive transition dominates in the spectrum, admitting the lack of inversion symmetry at Cs sites occupied by Eu3+. The spectrum of hypersensitive transition is expanded to the red part of spectrum due intense transitions terminating at higher-lying components of crystal-field-split 7F2 energy level. Obtaining chromaticity coordinates (0.669, 0.331)and absolute quantum yield (~21%) is possible using red phosphor based on monoclinic Y2O3:Eu3+.