Which river carries water from Lake Ontario toward the Atlantic Ocean?

The Saint Lawrence River carries water from Lake Ontario toward the Atlantic Ocean. It begins at Lake Ontario’s outflow near Kingston, Ontario, and Cape Vincent, New York, then flows northeast into the Gulf of Saint Lawrence.

The river is the principal drainage route for the Great Lakes, linking the continent’s vast freshwater system with the North Atlantic. Its course passes Montreal, Trois-Rivières and Quebec City; below Quebec City, the river becomes a broad tidal estuary before reaching the gulf.

The other options are rivers connected to the region but do not serve as Lake Ontario’s outlet. The Ottawa River joins the Saint Lawrence near Montreal, while the Saguenay enters farther downstream. The Hudson River is a separate Atlantic-draining river in New York and does not carry Lake Ontario’s water. “St. Lawrence” and “Saint Lawrence” are both standard forms of the name.