The Early Pleistocene is the key period for understanding the evolutionary history and paleobiogeography of rabbits (genus Oryctolagus). In Western Europe, many species were endemic, making them a reliable indicator of the evolution of the terrestrial ecosystems in which many species have evolved. However, the morphological variability of rabbit species is still poorly understood and their phylogeny remains a subject of debate. Through both qualitative (morphological description) and quantitative (linear measurements and two-dimensional geometric morphometrics) approaches, we address here the morphometric diversity of the third lower premolar (p3) – a tooth commonly used to distinguish leporid species – in order to assess intra- and inter-regional morphological variations in several Early Pleistocene rabbit populations. Our results suggest that the different approaches are complementary and allow, on different levels, a full characterisation of the p3 variability of Early Pleistocene rabbits and to imply relations between populations. The size and shape variations of this tooth reflect the taxonomic and phylogenetic signals of the different species but were probably also significantly impacted by geographic position and local climatic conditions. In view of the great morphometric variability highlighted in this work, we suggest a careful reconsideration of certain dental criteria previously considered "diagnostic" in the characterisation of these species. However, the overall results allowed us to discuss the phylogeny of the genus Oryctolagus and to hypothesise the ecological requirements and different phases of the dispersal of taxa in Western Europe, probably associated with global climate changes.