Neva River, a river in northwestern Russia. It flows from Lake Ladoga westward into the Gulf of Finland, an arm of the Baltic Sea. Though only 46 miles (74 km) long, the river carries a large volume of water, as it is the major outlet of the lake. It is part of a canal and river system linking the Baltic Sea to the White Sea and the Volga River system. St. Petersburg is near the mouth of the river.