The title compounds were synthesized at a temperature of 775 K via reaction of Fe2O3 with elemental cesium and rubidium alone or in combination with their hyperoxides AO2 where required by stoichiometry. The structures of the dark-red crystals have been determined by single crystal x-ray diffraction (Cs[FeO2]: cubic, space group Fd3m, a = 839.2(2) pm, Z = 8, R1 = 0.0547 and A5[Fe3O6] (A = Cs: orthorhombic, space group P212121, a = 861.8(2), b = 870.7(2), c = 1658.7(3) pm, Z = 4, R1 = 0.0617 and A = Rb: tetragonal, space group I4̅2d, a = 862.01(8), c= 1504.7(2) pm, Z =4, R1= 0.0334). These three compounds contain three-dimensional networks [FeO2], in the case of the ideal stuffed cristobalite composed of corner-sharing tetrahedra [FeO4/2], in the case of the new mixed valence compounds A5[Fe3O6] formed by corner-sharing of tetrahedra [FeIIIO4/2] and triangles [FeIIOO2/2] in a 1:2 ratio. The crystal structure of the cation rich compound Cs8[Fe2O7] (monoclinic, space group P21/c, a = 722.32(12), b = 1789.0(3), c = 733.88(12) pm, β =118.976(3)°, Z = 4, R1=0.0287) exhibits di-ferrate anions [Fe2O7]6− composed of two cornersharing [FeIIIO4] tetrahedra with a linear Fe-O-Fe bridge.