The space-confined growth by in-situ formed polysaccharides during hydrothermal process is successfully employed to fabricate ultrathin MoS2 nanosheets, which further evolve to MoS2/C evenly integrating nanosheets (2-4 nm) with conducting carbon after carbonization. The MoS2/C exhibits an excellent activity for hydrogen evolution reaction (HER) with a small onset overpotential of similar to 80 mV and a high current density of 88 mA cm(-2) at eta = 200 mV, which is associated with the enriched rim-sites on ultrathin MoS2 and the improved conductivity by carbon matrix. This work demonstrates that the ultrathin MoS2 nanosheets within carbon, possessing synergistically-enhanced activity and conductivity for HER, are feasible through the space-confined growth based on polysaccharide matrix, and this would open up new opportunities for exploiting highly efficient electrocatalysts. (C) 2014 Elsevier B.V. All rights reserved.