Presented are the first formal descriptions of mosasaur remains of Maastrichtian age from the Danish mainland (Jylland, Sjælland); just two taxa are recognised, viz. Mosasaurus cf. hoffmanni and Plioplatecarpus sp. Recent finds include an association of skeletal fragments, inclusive of a single marginal tooth crown, from within 10 metres or so of the K/T boundary near Holtug, Stevns Klint (Sjælland, eastern Denmark), here assigned to Plioplatecarpus sp. A brief review of previous records of Danish mosasaurs is added.