The Seine is a 777 km (483 mile) river in northern France. It rises at Source-Seine on the Langres plateau, about 30 km north-west of Dijon, and flows through Troyes, Paris and Rouen before reaching the English Channel between Le Havre and Honfleur. Its basin covers 78,910 km², including a small part of Belgium. About 78% of that land is farmed, and the basin contains Paris, Rouen, Le Havre and Reims. The Seine matters for the work it supports. Barges carry freight on it for 516 km, ocean-going ships reach Rouen 120 km inland, and the HAROPA port group at its mouth handles most of France's container traffic. A nuclear power station on its banks supplies about a third of the electricity used in the Paris region. And Paris began as a Gallic settlement on an island in the river.
The Parisii on the Île de la Cité, and the goddess Sequana
Paris takes its name from the people who first lived on the river there. The Parisii were a Gallic tribe that settled the banks of the Seine from around the middle of the 3rd century BC. One of the area's major north–south trade routes crossed the Seine on the Île de la Cité, and the island gradually became an important trading centre. The Parisii traded with river towns as far away as Iberia and minted their own coins. Julius Caesar recorded the town as Lutetia Parisiorum. Scholars disagree on what the tribal name meant: proposals include "cauldron", "the makers" and "spear people".
The river's own name goes back to a goddess. Offerings to Sequana, the Gallo-Roman goddess of the Seine, have been found at the source, where the remains of a temple lie buried. The Celtic word probably shares a Proto-Indo-European root, *seikw-, "to flow", with the English word "sea". The city of Paris has owned the source since 1864 and built an artificial grotto with a statue of a nymph there. The river also brought raiders. A Viking fleet sailed up it and sacked Paris in March 845, and Rollo led another attack on 25 November 885. Rollo later became Count of Rouen and the first ruler of Normandy.
Barges from Marcilly-sur-Seine: 516 km of working river
The Seine is easy to navigate because it falls so little. Paris lies 446 km from the sea, yet the river there is only 24 m above sea level. Commercial barges and push-tows can use it from Marcilly-sur-Seine all the way to the mouth, 516 km. Larger vessels can go upstream as far as Nogent-sur-Seine, through seven locks above the mouth of the Yonne. The Haute Seine between Montereau-Fault-Yonne and Paris is 98 km long with eight locks. Below Paris, smaller locks at Suresnes and Bougival take traffic down to the Oise confluence at Conflans-Sainte-Honorine, 72 km away, and four large multiple locks on the Basse Seine then lead to the tidal river.
Not every attempt to extend the waterway lasted. The 19th-century Canal de la Haute-Seine once let boats continue from Marcilly to Troyes, but it was abandoned in 1957. The river also has a place in the history of steam. On 9 August 1803, Robert Fulton tested his first successful steamboat on the Seine beside the Tuileries Garden. It was 66 feet long and made three to four miles an hour against the current.
Rouen and Le Havre: the ports at the mouth
The last 123 km, from Le Havre to Rouen, form the Seine maritime, the only part of the river used by ocean-going ships. The channel is dredged, and in the 1960s that dredging almost eliminated the tidal bore, the mascaret, on the lower river. Rouen grew rich on river trade and textiles from the 13th century and was a capital of the Anglo-Norman and Angevin rulers. Joan of Arc was burned there on 30 May 1431, and her ashes are said to have been thrown into the Seine from the Mathilde Bridge. The metropolitan area had 715,239 people in 2023.
King Francis I founded Le Havre, whose name means "the harbour", in 1517 on drained marsh at the river mouth. Allied bombing destroyed much of it in 1944. Auguste Perret's concrete reconstruction of 1945–1964 was inscribed by UNESCO as a World Heritage Site on 15 July 2005. The port is the largest container port in France and the second-largest port overall after Marseille. In 2011 it handled 68.6 million tonnes of cargo and about 60% of French container traffic, and in 2022 it handled more than 3 million containers. In 2021 the ports of Le Havre, Rouen and Paris merged into a single authority, HAROPA Port, so the whole river from the sea to the capital is now managed as one corridor. The commune had 166,462 residents in 2022. Our guide to the Port of Le Havre covers its terminals. Across the estuary, the small harbour at Honfleur was a transit point for goods from Rouen to England by the 12th century. Later its old dock drew Boudin, Courbet, Jongkind and Monet in the years before Impressionism.
Paris: 37 bridges and 240 bouquinistes
Paris is the largest community on the river. In January 2026 the city had an estimated 2.04 million people, and its metropolitan area had 13.3 million in 2023. The city has 37 bridges across the Seine. In 1137 a new marketplace, the forerunner of Les Halles, opened on the Right Bank, and the river-trade corporation based on the Place de Grève became, in effect, the first municipal government of Paris. UNESCO listed the riverbanks of central Paris as a World Heritage Site in 1991.
The bouquinistes are the best-known riverside trade. They are second-hand booksellers who rent fixed stretches of the stone parapet: on the Right Bank from the Pont Marie to the Quai du Louvre, and on the Left Bank from the Quai de la Tournelle to the Quai Voltaire. They moved onto the quays after the Council of State banned bookselling on the Pont Neuf in 1756. In 1859 the city gave them fixed pitches of 10 m of railing each, and the size of the boxes was set in 1930. Today some 240 bouquinistes use 900 green boxes holding around 300,000 old books. Before the 2024 Olympics, the authorities planned to remove the boxes for security. The booksellers campaigned against it, and President Emmanuel Macron ruled that they should stay, calling them part of the city's "living heritage".
Since 2002, the Paris-Plages scheme has closed riverside roads every July and August and put sand on them. It drew more than four million visitors in 2007.
Farmland, Troyes and the Nogent reactors on the upper Seine
Upstream of Paris the river supports quieter work. Most of the basin, 78% of it, is cultivated, and only 2% is forest. Troyes, on the Seine about 140 km south-east of Paris, was a stop on the Via Agrippa in Roman times and hosted the medieval Champagne fairs. Textile manufacturing was its main industry from the 18th century until the 1960s, and today it markets itself as the European capital of factory outlets. The commune had 62,088 people in 2023.
At Nogent-sur-Seine, 120 km south-east of Paris, the Nogent Nuclear Power Plant takes cooling water from the river for two 1,300 MWe reactors. It produces about a third of the electricity used in Île-de-France each year and employs around 700 permanent staff. The Seine has also been regulated to protect the capital. Four large storage reservoirs have been built since 1950 on the Seine and its tributaries the Yonne, Marne and Aube, among them the Lac d'Orient and the Lac des Settons. They help keep river levels steady, but they cannot stop major floods. The flood of January 1910 swamped much of Paris. In January 2018 the river reached 5.84 m at Paris on 29 January. A 2002 government report put the cost of a worst-case flood at €10 billion.
From three fish species in 1970 to swimming in 2025
The Seine-Normandy basin is under the heaviest human pressure of any river basin in France, and the river is poor at diluting what it receives. Sewage treatment plants began to be built in 1940. Even so, by 1970 about 60% of urban sewage still entered the river untreated, and the number of fish species fell to just three. After measures under the EU Water Framework Directive in the early 2000s, organic carbon, phosphorus and ammonium levels dropped. Atlantic salmon were reported back in 2009, and by the early 2020s 32 fish species were recorded near Paris.
Swimming had been banned since 1923. Jacques Chirac called for the ban to be lifted in 1988. In 2018 a €1.4 billion "Swimming Plan" began, including a storm basin to hold back the rainwater that overflows Paris's combined sewers. Mayor Anne Hidalgo swam in the river on 17 July 2024. During the Olympics, the river hosted marathon swimming and the triathlon swim, although water quality delayed the triathlon by a day. In July 2025 the Seine reopened to public bathing for the first time in almost a century. You can read more about the city that grew around the river in our guide to Paris, capital of France, or follow France's longest river in the Loire guide.