The Upper Magalloway River is a tributary of the Magalloway River. It flows for about 12 miles from its source at the outlet of Third Connecticut Lake near the Canadian border, to its confluence with the Second East Branch Magalloway River near the Maine state line. The river is part of the Androscoggin River watershed, which ultimately drains into the Atlantic Ocean.

Local roads off Dam Road (NH-16) are adjacent to the river.