Nanostructured carbon materials with high porosity and desired chemical functionalities are of immense interest because of their wide application potentials in catalysis, environment, and energy storage. Herein, a top‐down templating strategy is presented for the facile synthesis of functional porous carbons, based on the direct carbonization of diverse organic precursors with commercially available metal oxide powders. During the carbonization, the metal oxide powders can evolve into nanoparticles that serve as in situ templates to introduce nanopores in carbons. The porosity and heteroatom doping of the prepared carbon materials can be engineered by varying the organic precursors and/or the metal oxides. It is further demonstrated that the top‐down templating strategy is applicable to prepare carbon‐based single‐atom catalysts with iron‐nitrogen sites, which exhibit a high power density of 545 mW cm−2 in a H2–air proton exchange membrane fuel cell. A top‐down templating strategy is developed for facile engineering of heteroatom‐doped carbons and single‐atom catalysts, which is based on carbonizing a mixture of metal oxides and organic precursors. The resulting single‐atom catalyst exhibits a peak power density of 545 mW cm−2 in H2–air fuel cell testing, illustrating a considerable promise of this method for affording advanced functional carbon materials.