The hydrogen effect on room temperature creep of 310 S stainless steel was investigated by using nanoindentation. Hydrogen enhanced the primary creep of 310 S steel much more significantly compared with the steady-state creep, which was attributed to the interaction between hydrogen and dislocation. Hydrogen obviously decreased the indentation stress so as to promote the primary creep, while hydrogen had little effect on the steady-state creep due to the evolution from mobile dislocation to immobile dislocation. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.