The European-Asian taxon Placosaurus is a distinct glyptosaurine lizard that differs from the North American glyptosaurine genera Glyptosaurus, Helodermoides, Paraglyptosaurus, and Proglyptosaurus. Presently, species of Placosaurus can only be discriminated based on frontal morphology. Three species are recognized: Placosaurus rugosus Gervais, 1848–1952, Placosaurus estesi, sp. nov., and Placosaurus mongoliensis, all based on frontal material. Although the Asian species P. mongoliensis is retained in the genus Placosaurus, we consider this taxonomic assignment tentative. The species P. cayluxi, P. galliae, P. gaudryi, and P. margariticeps are considered nomina dubia. “Placosaurus” europaeus, based on a dentary with teeth, is tentatively retained in the genus Placosaurus but this generic assignment is equivocal. The species “P.” quercyi pertains to a new ‘melanosaurin’ and not to Placosaurus.