This study investigated the effects of hydrostatic compressive stress in retained austenite (RA) on mechanical properties and hydrogen embrittlement (HE) of the martensitic steels. It was found that a high hydrostatic compressive stress in RA, which was produced by the martensitic transformation, lead to an improvement of ductility for the steels without hydrogen. However, the mechanical properties were different after hydrogen charging. The low hydrostatic compressive stress in RA had little effect on HE resistance, but the high hydrostatic compressive stress (231 MPa) induced the twinning of RA and resulted in the aggravation of the HE sensitivity. Moreover, the detwinning of RA via tempering improved the HE resistance. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.