Investigation on meteorites has suggested that the Martian core comprises an Fe or Fe-Ni alloy with sulfur identified as the primary light element. The InSight mission data analysis revealed a larger and less dense Martian core than previously estimated, indicating the significant involvement of additional lighter elements. Recent studies have considered hydrogen (H) as a light element candidate for the Martian core. However, the co-alloying behaviors of S and H in Fe metal at the Martian core conditions are not well understood. This study investigates the influences of H and its amount on phase relations in the Fe-S systems under the relevant pressure-temperature conditions. Our experiments reveal that the reaction products between FeS/Fe3S and H vary with H concentration. With a small amount of H (≤ 0.6 wt% H), Fe3S exhibits stability at 30 GPa but partially decomposes at 40 GPa. At higher H concentration (∼0.14 wt%), Fe3S reacts with H, yielding FeHx, FeS (VI), FexS (x = 1/2, 3/2, or 2), and FeSxHy . For the Fe1−δS–H system, both FeS and FeS2 appear regardless of the H content of ≤0.07 wt%, while FeHx forms only in higher H concentrations (0.07 wt% H). This study sheds light on the interplay of S and H for Fe metal, offering important insights for possible Martian core mineralogy across various compositional scenarios.