The presence and origin of the mygalomorph spider genus Ummidia Thorell 1875 in the western Mediterranean region is reconsidered. The traditional idea, expressed in the works of Walckenaer and Simon, that Ummidia is a recent American import in the Mediterranean region, is opposed by the observation that at least four distinct Ummidia species inhabit different geographical areas within the western Mediterranean. The taxonomical revision of the Mediterranean Ummidia fauna presented here results in the description of one new species (Ummidia algarve n. sp.), the removal of U. picea Thorell 1875 and U. algeriana (Lucas 1846) from synonymy with U. aedificatoria (Westwood 1840) and the placing of U. occidentalis (Simon 1909) in synonymy with U. aedificatoria (Westwood 1840).