Seine River, Seine River© Tupungato/Shutterstock.comriver of France, after the Loire its longest. It rises 18 miles (30 kilometres) northwest of Dijon and flows in a northwesterly direction through Paris before emptying into the English Channel at Le Havre. The river is 485 miles (780 kilometres) long and with its tributaries drains an area of about 30,400 square miles (78,700 square kilometres).