Mercury (Hg) records in marine and terrestrial archives across the Cretaceous/Paleocene (K/Pg) boundary were examined as a proxy for Deccan Large Igneous Province (LIP) eruptions. We examined no less than twenty-six key sections/boreholes that are globally distributed, and show that Hg values have a log-normal distribution. The data have a similar trend to that across other major extinction boundaries in the Phanerozoic record. Ques-tionable Hg/TOC anomalies have been ruled out, indicating excess Hg loading at the K/Pg boundary. Most Hg isotope values across the K/Pg boundary indicate a volcanic Hg source, based on the mass-independent (MIF) Delta 199Hg values. However, negative Delta 199Hg values suggest continental inputs in the Jhilmili section (India). Near -synchronous Hg and negative carbon-isotope excursion (CIE) patterns are identified in sediments associated with LIPs representing the paired release of Hg and isotopically depleted CO2, especially in the Latest Maastrichtian warming event (LMWE) that we attribute to the Deccan LIP. We compared the response of global biotic changes to Deccan volcanism and the Chicxulub impact. It appears that the end-Cretaceous mass extinction was a complex catastrophe caused by volcanism driving major climate fluctuations and ocean acidification, and perhaps exacerbated by the Chicxulub impact.