Realization of macroscale three-dimensional isotropic carbons that retain the exceptional electrical and mechanical properties of graphene sheets remains a challenge. Here, a method for fabricating graphene-derived carbons (GDCs) with isotropic properties approaching those of individual graphene sheets is reported. This synthesis scheme relies on direct cross-linking of graphene sheets via the functional groups in graphene oxide to maximize electronic transport and mechanical reinforcement between sheets and the partial restacking of the sheets to increase the material density to about 1 g cm(-3). These GDCs exhibit properties 3-6 orders of magnitude higher than previously reported 3D graphene assemblies.