Map of the Roman Empire - Seine River

Seine River
D-1 on the Map

Ancient Seine River A river known in the Roman world as the Sequana, it was one of the main rivers of the Gauls. The Sequana River flowed through the province of Gallia Lugdunensis into the Atlantic ocean across from Britain.

Seine. The name "Seine" comes from the Latin Sequana, a Latinisation of the Gaulish (Celtic) Sicauna, which is argued to mean "sacred river".  - Wikipedia

Sequana fl., a r. of Gaul, rising towards Andematunum and falling into the Atlantic at Carocotinum. Seine. - Classical Gazetteer

Sequăna (Σηκοάνας). Now the Seine; one of the principal rivers of Gaul, rising in the central parts of that country, and flowing through the province of Gallia Lugdunensis into the ocean opposite Britain. It is 346 miles in length. Its principal affluents are the Matrona (Marne), Esia (Oise), with its tributary the Axona (Aisne), and Incaunus (Yonne). This river has a slow current, and is navigable beyond Lutetia Parisiorum (Paris) (B. G. i. 1; Ptol.ii. 8, 2).  - Harry Thurston Peck. Harpers Dictionary of Classical Antiquities. New York. Harper and Brothers. 1898.

Sequana
SE�QUANA (Σηκουάνας, Σηκοάνας, Ptol. 2.8.2), the Seine, one of the large rivers of Gallia. The Seine rises in the highlands south of Langres, but in the department of C�te d'Or, and flows in a northwest direction past Ch�tillon-sur-Seine, Troyes, Meleun, Paris, Mantes, Elboeuf, Rouen, and Le Havre. It enters the Atlantic below Le Havre. The course of the Seine is about 470 miles, and the area of its basin is about 26,000 English square miles, which is only one half of the area of the basin of the Loire. The chief branches of the Seine which join it on the right bank are the Aube, the Marne, and the Oise; on the left bank, the Yonne, the Loing, and the Eure. None of the hills which bound the basin of the Seine, or are contained within it, have a great elevation, and a large part of the country included within this basin is level.

Caesar (Caes. Gal. 1.1) makes the Sequana and the Matrona (Marne) the boundary between the Celtae and the Belgae. Strabo (iv. p.192) says that the Sequana rises in the Alps, a statement which we must not altogether impute to an erroneous notion of the position of the river's source, though his knowledge of Gallia was in many respects inaccurate, but to the fact that he extended the name of Alps far beyond the proper limits of those mountains. But his inaccuracy is proved by his saying that the Sequana flows parallel to the Rhine, and through the country of the Sequani. He is more correct in fixing its outlet in the country of the Caleti and the Lexovii. The Seine was navigated in the time of Strabo and much earlier. [GALLIA TRANSALPINA Vol. I.]

The M�trona, as Ausonius names it (Mosella, 5.462),-- �Matrona non Gallos Belgasque intersita fines,�--joins the Seine a few miles above Paris; it is the largest of the affluents of the Seine.

Ammianus Marcellinus (15.11) says that the [p. 2.966]united streams of the Sequana and Matrona entered the sea near Castra Constantia (Coutances), which is a great mistake. In the cosmography of Aethicus the Sequana is named Geon or Geobonna. - Dictionary of Greek and Roman Geography (1854) William Smith, LLD, Ed.