The geometries and bonding properties have been predicted for cyclic AlS2 and GaS2 species at DFT, MPn (n = 2, 3, 4), QCISD(T) and CCSD(T) levels with the 6-311 + G (*) basis set. Harmonic vibrational frequencies were determined using DFT and MP? methods. The relevant energies were calibrated at high-order electron correlation levels. Each species possesses a (2)A(2) ground state with a higher-energy (2)A(1) state, lying 7.2 kcal/mol for AlS2 or 20.0 kcal/mol for GaS2 above at CCSD(T)/6-311 + G (*) level, and the corresponding CCSD(T) dissociation energies are 64.0 (AlS2: (2)A(2)) and 59.0 kcal/mol (GaS2: (2)A(2)), respectively. Analysis indicates that the cyclic AlS2 and GaS2 should be classified as supersulfide, but they are not as ionic as NaO2 and less ionic than AlO2.