Richelieu River, a river in southern Quebec, Canada. A link in the waterway connecting New York City and Montreal, the river was an important route for early explorers and is used today to ship large amounts of manufactured goods. Leaving the north end of Lake Champlain, the Richelieu flows north for about 80 miles (130 km). At Sorel it enters a widening of the St. Lawrence River called Lake St. Peter.

The Richelieu was discovered in 1609 by Samuel de Champlain and was named for Cardinal Richelieu of France in 1642. In the 19th century, canals were built to bypass rapids at Chambly and St. Ours.