The Strait of Bonifacio is the channel between the French island of Corsica and the Italian island of Sardinia, 11 km (6.8 mi) wide at its narrowest and no more than about 100 m deep, which links the western Mediterranean and the Sea of Sardinia to the Tyrrhenian Sea. It takes its name from Bonifacio, Corsica's southernmost town, founded as a citadel by Boniface II, Margrave of Tuscany, in 828. It matters because it is the direct sea route between the western Mediterranean and the Tyrrhenian Sea, and because its granite reefs, shoals and winds have made it notorious among sailors, so much so that since 1993 France and Italy have closed it to their own ships carrying dangerous goods.
The best way to understand the strait is to sail it. This guide follows a boat from the open sea west of the strait, past the cliffs of Bonifacio and the Lavezzi islands, through the narrows to Santa Teresa Gallura, and out among the Maddalena islands into the Tyrrhenian, naming what lies on each shore along the way.
Approaching From the Gulf of Asinara and the Sea of Sardinia
A ship coming from the Balearics or the Gulf of Lion approaches the strait across the Sea of Sardinia, with the Gulf of Asinara opening on its right as it nears northern Sardinia. Before it enters, it must report on VHF channels 16 and 10 to the control station on Maddalena Island in Italy, because a traffic separation scheme governs the strait and westbound and eastbound ships answer to different authorities. Ships heading east to west report instead to the station at Pertusato on the French side.
The rules are strict because of a bad record. After a tanker disaster in 1993, France and Italy barred ships flying their own flags from carrying dangerous goods through the strait; vessels under other flags carrying such cargo are strongly discouraged and must take a pilot. The two countries then agreed to work towards an international marine park covering the strait, taking in part of the Maddalena islands, and in 1999 France created its share as the Bouches de Bonifacio nature reserve. That French portion alone covers 794.6 km², about 300 ha of it land and the rest sea, which makes it the largest nature reserve in metropolitan France.
The weather explains the caution. The mistral, the cold northwesterly wind that blows down the Rhône valley into the Gulf of Lion, reaches as far southeast as Corsica and Sardinia and often whips up sudden storms between Corsica and the Balearics. It averages about 50 km/h when it blows and sometimes reaches 100 km/h.
Under the White Cliffs of Bonifacio
The first landmark on the Corsican shore is the town that names the strait. Most of Corsica is granite, but around Bonifacio the southern coast is an outcrop of chalk-white limestone, carved by the sea into overhanging cliffs about 70 m high. Houses in the old upper town stand on the very lip of the precipice, so that from the water they seem to hang over it. The harbour lies in the Bay of Bonifacio, a drowned ravine of fjord-like appearance, sealed off from the sea by a finger of rock 1,500 m long and 200 m wide. In the low sea levels after the last ice age, when Corsica and Sardinia were joined, this ravine was a valley leading up into the Corsican highlands. The harbour takes ships of up to 3.5 m draught, ample for ancient vessels and modern small craft.
People have used this route for a very long time. The rock shelter of Araguina-Sennola, just north of the town, held the burial known as the Lady of Bonifacio, carbon-dated to about 6570 BC, and chert from Monte Arci in Sardinia found at local sites shows that goods were already crossing the strait in the Neolithic. The round tower called Il Torrione survives from the original 9th-century citadel. Bonifacio is the southernmost commune of metropolitan France and lies closer to the capitals of 20 other countries than to Paris.
Cape Pertusato and the Granite Reefs of Lavezzi
About 9 km east of the harbour, the boat passes Cape Pertusato, the southernmost point of the island of Corsica, topped by a lighthouse. Some historians identify it with Marianum Promontory, the southern tip of Corsica named by the geographer Ptolemy. Beyond it, the strait's most dangerous ground begins.
The Lavezzi archipelago is a scatter of small granite islands and reefs about 4 km off the Corsican mainland, 7 km from Cape Pertusato and 10 km southeast of Bonifacio. Its highest point is only 50 m, and it holds the southernmost point of metropolitan France. Cavallo, of about 112 ha, is the only inhabited island; Lavezzu, of 66 ha, lies just to its south, and the islets of Piana, Ratino, Porraggia and Sperduto complete the group from west to east.
These reefs caused the worst disaster in the strait's history. On 15 February 1855 the French frigate Sémillante, which had left Toulon the day before carrying troops to the Crimean War, was driven onto a reef in a storm and sank. None of the roughly 750 soldiers aboard survived, and two memorial cemeteries on Lavezzu hold the remains of the victims. Today the islands are better known for their seabirds: between 255 and 400 pairs of Scopoli's shearwaters breed on Lavezzu each year, and their breeding success has risen since black rats were eradicated from the island in 2000.
Across the 11 km Narrows to Santa Teresa Gallura
Past Lavezzi the boat reaches the narrowest part of the strait, where only 11 km of water separates the two islands. Somewhere in that channel it crosses an international border. The France–Italy Maritime Boundary Agreement, signed in Paris on 28 November 1986 and in force since 15 May 1989, draws a line about 40 nautical miles long through the strait, made of five straight segments between six fixed points and set at roughly equal distance from each coast. There is no bridge or tunnel; the crossing between Corsica and Sardinia is made by ferry.
On the Sardinian side the first town is Santa Teresa Gallura, on the northern tip of the island, with a permanent population of 5,144 in 2026 that rises to between 10,000 and 15,000 in the summer season. From its beach, Rena Bianca, the southern coast of Corsica is in plain view. The town is one of several candidates for the site of Tibula, a Roman-era settlement whose exact location is unknown.
Among the Seven Islands of La Maddalena
East of Santa Teresa the strait fills with islands again. The Maddalena archipelago has seven main islands: La Maddalena, Caprera, Spargi, Santo Stefano, Santa Maria, Budelli and Razzoli, with many smaller islets. Only La Maddalena, Caprera and Santo Stefano are inhabited, and the whole group forms the comune of La Maddalena, home to 10,449 people in 2026. It is protected as the Arcipelago di La Maddalena National Park and was placed on UNESCO's tentative World Heritage list in 2006. Car ferries run to La Maddalena from Palau on the Sardinian coast, and only La Maddalena and Caprera have roads.
The islands record most of the strait's history. The Romans called them Cunicularia and their waters were busy with shipping in the 2nd and 1st centuries BC. Pisa and Genoa fought over them in the 13th century; after a long abandonment they were resettled in the 18th century by Corsican shepherds and settlers from Sardinia. In 1793 a French expedition that included the young Napoleon Bonaparte tried and failed to take La Maddalena, his first experience of combat. During the Napoleonic Wars, Admiral Horatio Nelson used the archipelago as a base for his fleet against the French.
Caprera, the second-largest island at 15.7 km², with 45 km of coastline, probably takes its name from its wild goats (capra in Italian). Giuseppe Garibaldi retired there in 1854 and lived on the island until his death in 1882. To the northwest, Budelli, just 1.6 km² and rising to 87 m at Monte Budello, is known for a beach whose sand is pink from the shell fragments of a tiny marine organism, Miniacina miniacea; scenes of Michelangelo Antonioni's film Red Desert were shot there for its 1964 release, and the island had a single caretaker until 2021. Santo Stefano tells a Cold War story: from 1973 until 2008 it housed a NATO naval base for US nuclear submarines, and in 2003 the USS Hartford ran aground near Bisce Island during manoeuvres.
Out Into the Tyrrhenian Sea
Beyond Caprera the channel opens and the boat leaves the strait for the Tyrrhenian Sea, the basin that stretches east to the coasts of Tuscany, Lazio and Campania. Looking back, the passage that took only a few hours shows its whole character: limestone at Bonifacio, granite on Lavezzi and in the Maddalena islands, and two nations sharing a channel narrow enough that a person standing on a Sardinian beach can make out the buildings of a French town.
Weather here follows the Mediterranean pattern. At Bonifacio, Météo-France records an annual average of 582.2 mm of rain, with November the wettest month at 89.2 mm and July the driest at 7.1 mm; the mean temperature peaks at 24.8 °C in August and falls to 10.5 °C in February. The dry summer is when Santa Teresa's population doubles or triples and the islands fill with boats; the four months from October to January bring more than half of the year's rain.
For the land on either side of the narrows, read our guides to Corsica and to Sardinia, the two granite islands the strait divides.