Proti is an uninhabited island to the west of Marathopolis in Messinia. It is speculated that its name comes from Proteus, a deity of the sea. According to other approximations, the origin of the name might come from the fact that Proti (meaning "first" in Greek) is the first part of land that one might see, approaching the shores of Messinia from west by sea. Others still say its name comes from the word 'Ploti' ("πλωτή” in Greek, meaning 'afloat'), indicating the deep waters that surround the island. Thucydides mentions it as a station of the Athenian fleet, which dropped anchor on one of the island's coves to shelter itself from a storm, on its way to Sphacteria (where the Athenians lay siege on the few numbers of the Spartan guard). It was inhabited in ancient times, though, a fact that is made evident by the ruins of the Mycenaean period (such as an acropolis with a wall and a circular tower).

There was a temple devoted to the goddess Artemis on the island, on top of which the people built a small chapel devoted to the Virgin Mary. It is said that the island has been a place of refuge to infamous pirates and corsairs, Saracens as well as from Mani, in a time when the populace of Mani turned to piracy to survive. That is the source of a legend that tells of hidden pirate treasures buried on the island. There are also some messages carved on rocks, wishing the sailors “good luck”, which add to that legend. These messages are preserved to this day, on some parts of the rocks. In reality, these writings date back to the ancient and Byzantine times, and are nothing more than the wishes of sailors for salvation, carved when they sought shelter on the shores of the island, trying to save themselves from storms.

Nowadays, a visitor on the way to Marathopolis from Filiatra, upon nearing the shores, will spot Proti on the horizon, giving the impression of an unusual or scary shape which resembles a monster or a crocodile at first. The island houses the Monastery of the Assumption of Mary ('Kimisi tis Theotoku Gorgopigis'), which was built to house the miraculous icon depicting the Virgin Mary, that was found on the rocks. The monastery celebrates two holidays every year, on the 23^rd of August and the 24^th of September. The residents and visitors can reach the island by boat to take part in the festivities, which include meals made of fresh fish. Since it is characterized by very steep and tall rocks, Proti offers many opportunities for climbing and also hiking along its ancient paths, while its calm beach 'Vurlias' is ideal for an enjoyable swim. Another fascinating experience that Proti offers is diving, as it is the host of considerable underwater wealth - which even contains a shipwreck. The boats that ferry visitors to the island depart from Marathopolis.