Messinia, a prefecture in the Peloponnese and one of its most important areas historically and culturally, covers the southwestern tip of the Peloponnese, bordering with the regional units of Ilia to the north, Laconia to the east and Arcadia to the northeast.

The eastern part of the county is taken up by the imposing mountain of Taygetus, which constitutes a natural border between Messinia and the prefecture of Laconia. The highest summits of Taygetus (Prophitis Ilias 2,407 m, Neraidovouna 2,025 m, Xerovouna 1,852 m) are located precisely on the boundary between the two counties. At the center of the prefecture, among the mountains, lies the fertile valley of Messinia, with plentiful waters, both above and below the ground. Smaller valleys are formed on the Ionian coast, in Kyparissia, Filiatra, Gargaliani, Pylos and Methoni.

On the south is the Messinian Bay and on the west, on the Ionian Sea, the Gulf of Kyparissia. The Messinian coastline is very interesting in its variety: The eastern part of the Messinian Bay is rocky and slightly dismembered, creating a unique landscape. Across the bay's coast we come across coves such as that of Kardamyli, Kitries, Almyros and Petalidi, and capes such as that of Koroni and Akritas. To the south there is the island complex of the Messinian Oinousses, comprising Venetiko, Schiza, Aghia Mariani and Sapienza, areas of unique beauty and ecological significance, and to the north we come across the historical bay of Navarino, with the islet of Sphacteria sprawled at its entrance. 

The longest river that runs through Messinia is Pamisus, which springs from the western slopes of Mount Taygetus and flows into the Messinian Bay. There are also smaller rivers, such as Velikas and Nedon, which springs from the mountainous Alagonia and flows into the sea of Kalamata.