Two novel superhard 3D sp³ hybridized carbon allotropes (Cmmm-C₃₂ and P6/mmm-C₅₄) are proposed in this work through first-principles calculations. Both Cmmm-C₃₂ and P6/mmm-C₅₄ have a honeycomb structure. P6/mmm-C₅₄ shows a wide direct bandgap (3.564 eV), while Cmmm-C₃₂ shows an ultrawide indirect bandgap (5.051 eV), as determined using the HSE06 hybrid functional. The hardnesses of Cmmm-C₃₂ and P6/mmm-C₅₄ are 83.72 and 54.01 GPa, respectively, and their calculated ideal strengths further confirm their superhardness characteristics. P6/mmm-C₅₄ is isotropic in the (001) plane. The minimum thermal conductivities of Cmmm-C₃₂ and P6/mmm-C₅₄ are larger than those of diamond-C, illustrating that Cmmm-C₃₂ and P6/mmm-C₅₄ are potential semiconductor device materials.