The Seine is a river in France. It flows into the English Channel between Le Havre and Honfleur. It is long. It is the second-longest river in France. Other important cities along its course are Paris, Troyes and Rouen. Its drainage basin has a surface of . The Seine starts in Source-Seine, in Côte-d'Or, Bourgogne-Franche-Comté, at an height of .