The ferromagnetic intermetallic compound Mn2Ga5 has been synthesized and characterized by single-crystal X-ray diffraction study and by magnetic property measurements. The compound, with the Mn2Hg5-type structure, exhibits a saturated magnetic moment of 2.71 muB per formula unit with T(C) approximately = 450 K. The electronic structure of the compound was analyzed by employing FPLO, LMTO, and the extended Hückel tight-binding calculations. The nonmagnetic electronic structure of Mn2Ga5 reveals remarkably flat degenerate (superdegenerate) bands in the vicinity of the Fermi level but only in the a*b*-plane of the Brillouin zone. The resulting high density of the states at the Fermi level, DOS(E(F)), is consistent with the Stoner condition for the observed itinerant electron ferromagnetism. Detailed orbital analysis shows an intriguing structure-magnetism correlation, as the superdegeneracy is found to be a consequence of the unique atomic arrangement and bond angles in the structure.