A novel rapid fabrication method was developed for the first time to prepare hollow manganese oxide nanotubes with porous walls, using sacrificial carbon nanotube templates. Multiwalled carbon nanotubes (CNTs) are coated with amorphous manganese oxide layers by acidic reduction of potassium permanganate solution. The rapid synthesis process with the evolution of gaseous byproduct yields very high porosity in the coated manganese oxide layers. Subsequent heat treatment leads to the removal of CNT templates, resulting in the formation of amorphous and crystalline hollow manganese oxide nanotubes with highly porous walls. The porous hollow nanotubes were found to provide excellent catalytic performances in the degradation of organic dye at ambient conditions by virtue of the very high surface reaction sites within the porous hollow tubular structures. These novel nanostructures of hollow nanotubes with porous walls are promising for a series of applications such as hydrogen storage, sensing, supercapacitance, and catalysis, among others.