This study includes sample name, depth with respect to the Cretaceous-Paleogene (K/Pg) boundary (cm), percentage of calcium carbonate (%CaCO3), percentage of total organic carbon (%TOC), stable carbon isotope composition of bulk carbonate (d13Ccarb), stable oxygen isotope composition of bulk carbonate (d18Ocarb), stable carbon isotope composition of bulk organic carbon (d13Corg), stable nitrogen isotope composition of bulk organic matter (d15N), and stable carbon isotope composition of phytane (d13Cphytane) for 8 K/Pg boundaries in Tunisia (El Kef and Aïn Settara), Spain (Caravaca and Agost), France (Loya and Bidart, and Denmark (Kulstirenden and Højerup). The standard deviation for each parameter is reported when multiple analyses of the same sample were performed. Analytical reproducibility (1σ) was calculated as better than 0.1% for TOC and TN, 0.1‰ and 0.5‰ for d13Corg and d15N, and 0.04‰ and 0.09‰ for d13Ccarb and d18Ocarb by comparison with analytical standards (see main text for details).