Monte Arcosu is a mountain in the Sulcis massif, in southern Sardinia, Italy. It has an elevation of 948 metres (3,110 ft).
The mountain has a characteristically truncated cone shape, resulting from the differential erosion which followed its formation during the Variscan orogeny. The massif is formed by a granitic intrusion from the Carboniferous, lying on a Paleozoic schist basement and in turn surmounted by Paleozoic scists[check spelling]. The Variscan orogeny removed the upper schist layer from all the massif's peaks but Monte Arcosu, modelling it and showing the granite along the steep slopes.