In this work, a facile hydrothermal method has been developed to synthesize a three-dimensional porous birnessite manganese dioxide hierarchical structure (pMHs) using thermally reduced graphene oxide paper as a sacrificing template. The morphology, microstructure, and thermal stability of the obtained samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, N₂ adsorption–desorption isotherms, and thermal gravimetric analysis. Furthermore, the electrochemical properties of the pMHs as an electrode material for supercapacitor were investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy in 1 M Na₂SO₄ electrolyte, and a specific capacitance of 194 F g⁻¹ was achieved at a current density of 0.1 A g⁻¹. The long-term stability implies that the synthesized pMHs is a good candidate as an electrode material for SCs.