Three-dimensional graphene-based structures such as graphene aerogels or foams have shown applications in energy, environmental matters, and many other areas. Here, we present a method to convert raw cotton into functional aerogels containing a significant amount of nitrogen-doped graphene (N-graphene) sheets grafted on carbonized cellulose fibers. Urea was introduced into raw cotton as a molecular template as well as a nitrogen source to synthesize mushroom-like N-graphene sheets strongly attached to cotton skeletons. The excellent processability of raw cotton allows us to configure bulk or meter-long fiber shaped aerogels, with high porosity and flexibility. Synergistic effects stemming from the integration of N-graphene and carbonized cotton skeletons promise potential applications as conductive electrodes for supercapacitors, with a measured specific capacitance of 107.5 F g(-1) in a two-electrode system. Our results indicate a low-cost and scalable approach toward high-performance graphene-based aerogels and electrodes via biomass templating.