Warm rolling at 473 K with total reductions up to 65% significantly strengthened a 304 L austenitic stainless steel. The tensile strength at room temperature increased from 600 MPa to 1040 MPa. Outstanding mechanical properties of the warm rolled steel were observed at 77 K, when the ultimate tensile strength of 1830 MPa and a fracture elongation of 39% were achieved. Moreover, the warm rolled steel exhibited high impact toughness, especially, at cryogenic temperature that was attributed to the crack branching crosswise to the principal crack direction.