Elafonissos Island is part of the western arm of the horseshoe defining the Neapoli bay, in southern Peloponnese. The small island is facing the eastern side of the bay, materialised by the massive promontory of Malea. The western side of the bay was, in antiquity, was united to the land and constituted a real peninsula that enclosed the open yet sheltered bay of Neapoli, one of the best known sea refuges for the ships sailing the channel between Cape Malea and Kythera Island.

As a peninsula Elafonisos was named Onou Gnathos, referring to its resemblance to a donkey jaw. At the base of the "jaw" and around Pavlopetri islet, an important city prospered in prehistoric period, now submerged by the sea.

The main morphological characteristic of Elafonisos is its mild terrain. The highest point is the peak Vardia (276m), other high points are Varditsa (144m), Vigla (134m) and Silos (178m).