Port-Cros is a French island in the Mediterranean island group known as the Îles d'Hyères. It is part of the commune of Hyères, and part of the department of Var in the region of Provence-Alpes-Côte d'Azur. The island was donated to the French government with the promise that a national park, the Port-Cros National Park, would be created on the island. This was established on December 14, 1963. The island is 4 km wide and its most elevated point is 199 meters. It is 650 hectares.
The island was known as Messea (Middle Island) to the ancient Greeks. Its present name derives from the small port on the island, which is cross-shaped. Roman tombs on the island indicate that there may have been a Roman colony on the island, and coins and canals of Roman origin have also been found on the island. In the 5th century, the monastery of Lérins established a branch on the island of the Levant, and this foundation on Levant established a branch on Port-Cros in the small valley of Notre-Dame. This monastery on Port-Cros was destroyed by Barbary pirates, who repeatedly attacked the Hyères Islands from the 10th to the 16th centuries.
In 1531, François I of France visited the Hyères, and as a result of being informed by inhabitants of the pirate attacks, charged Bertrand d'Ornesan with the task of constructing fortifications on the islands to defend them against pirates. He elevated the three islands to the status of a marquisate on February 13, 1532. In 1549, this marquisate passed to Christophe de Rocquendorf. To attract colonists, he granted asylum to common law criminals, but these caused as much disorder as the pirates they were meant to be a shield against. In 1617, the promised fortifications had not yet been built, but under the direction of Cardinal Richelieu, construction began with the building of the Tour de l'Éminence, the fort of l'Estissac and the fort at Port-Man. Louis XIV of France fought against piracy in the region, but the lack of a substantial garrison caused the British to plunder Port-Cros in 1700 and to invade in 1742 before being driven out by the Jean-Frédéric Phélypeaux, Count of Maurepas.