The Elk River is a tidal tributary of the Chesapeake Bay on the Eastern Shore of Maryland and on the northern edge of the Delmarva Peninsula.
The canal and river now serve as one boundary of the Elk Neck Peninsula.
Little Elk Creek rises near Oxford, Pennsylvania, and the East Branch and West Branch of Big Elk Creek rise to the south of Cochranville, Pennsylvania.
They descend through the Pennsylvania and Maryland Piedmont, before reaching sea level at Elkton, the head of navigation.
On the eastern shore major tributaries are Back Creek, much of which is now the Chesapeake & Delaware Canal, and the Bohemia River.