Free-standing flexible mesoporous graphene-sulfur nanocomposite electrodes have been prepared by a sulfur vapor treatment approach. Amorphous sulfur homogeneously was distributed in the mesoporous architectures of porous graphene paper, in which sulfur was immobilized. The as-prepared mesoporous graphene-sulfur papers can be directly applied as electrodes in lithium-sulfur batteries without using a binder, conductive additives or an extra current collector. The conductive flexible porous graphene networks can effectively facilitate electron transfer and electrolyte diffusion. The free-standing sulfur-graphene nanocomposite electrodes achieved a high discharge capacity of 1393 mA h g-1 with an enhanced cycling stability and good rate performance. © The Royal Society of Chemistry 2013.