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The composition of a planet’s core has important implications for the thermal and magmatic evolution of that planet. Here, we conducted carbon (C)solubility experiments on iron-silicon (Fe-Si)metal mixtures (up to 35 wt%(~52 atom%)Si) at 1 GPa and 800–1800°C to determine the carbon concentration at graphite saturation (CCGS) in metallic melt and crystalline metal with varying proportions of Fe and Si to constrain the C content of Mercury’s core. Our results, combined with those in the literature, show that composition is the major controlling factor for carbon solubility in Fe-rich metal with minimal effects from temperature and pressure. Moreover, there is a strong anti-correlation between the abundances of carbon and silicon in iron-rich metallic systems. Based on the previous estimates of <1–25 wt% Si in Mercury’s core, our results indicate that a carbon-saturated mercurian core has 0.5–6.4wt% C, with 6.4wt% C corresponding to an Si-free, Fe core and 0.5wt% C corresponding to an Fe-rich core with 25 wt% Si. The upper end of estimated FeO abundances in the mantle(up to 2.2 wt%)are consistent with a core that has <1 wt% Siand up to 6.4 wt% C, which would imply that bulk Mercury has a superchondritic Fe/Si ratio. However,the lower end of estimated FeO (≤ 0.05 wt%) support CB-chondrite like bulk compositions of Mercury with core Si abundances in the range of 5–18.5 wt% 33 and C abundances in the range of 0.8–4.0 wt%.