Current assessments show the highest diversity of terrestrial Isopods is within Mediterranean Biomes and insular tropical regions. Despite our growing understand of terrestrial Isopod biogeography, there has been liSle research examining the speciaOon mechanisms behind the high diversity within these parOcular regions. We chose the genus Armadillidium within the Mediterranean Basin as a model system, focusing on the French fauna, parOcularly those represented in the occidental-subgroup of the maculatum species group. We sequenced the mitochondrial CO1 gene and nuclear CDS, and collated morphological and biogeographic data to examine the family placement of the Armadillidium, the relaOonship of the species-groups and invesOgated the evoluOonary history of the maculatum-group in France. Our results support other findings that Armadillidium is polyphyleOc. Species with duplocarinate-type cephalons belong to undiagnosed genera with evoluOonary origins within the Iberian peninsula. The maculatum-group is also polyphyleOc with only 4 members of the subgroup having a shared origin, likely during the Miocene. We tentaOvely Oed the diversificaOon of the subgroup to three major geological events: the formaOon of the Molasse basin, development of rias aher the Massinian Salinity Crisis and climaOc oscillaOons of the Pliocene. Two modes of allopatry were idenOfied relaOng to these geological events, in addiOon to parapatry linked with petrological change. Our findings suggest the geological heterogeneity and dynamic history of the conOnent is responsible for diversificaOon within the occidental-subgroup. However, other possible contributors to diversificaOon have been idenOfied, which likely correlate with the adapOve characterisOcs of terrestrial Isopods.