An almost complete mandible from the Lower Pliocene deposits of Arcille (Tuscany) is described and investigated for the first time. The specimen is assigned to Pliorhinus megarhinus, which is documented in Italy from the latest Miocene to the mid-Pliocene. The studied specimen is larger than Stephanorhinus etruscus and S. jeanvireti, and morphologically fits P. megarhinus from the Early Pliocene of Montpellier (France), Vera Basin (Spain) and Val di Pugna Fangonero (Italy). This specimen represents the first stratigraphically well-documented Pliocene record of this species in Italy, the previous discoveries dating back to the 19th century or the beginning of the 20th century, hence lacking stratigraphic control. According to the obtained results, it is possible to assess the occurrence of P. megarhinus during the earliest Pliocene in Italy as well as to confirm the long-lasting persistence of this species, whose fossil record covers a timespan between 6.7 Ma and 3.5 Ma. During that time, P. megarhinus did seemingly undergo a trend of body mass reduction.