The Wicomico River is a 13.0-mile-long (20.9 km)[1] tributary of the lower tidal portion of the Potomac River located in the U.S. state of Maryland south of Washington, DC.

The river empties into the Potomac at Cobb Island and St. Margaret's Island.

Its watershed area (excluding water) is 77 square miles (200 km2), with 2% impervious surface in 1994[2] in Charles, St. Mary's, and southern Prince George's counties.

The lower section of the river forms part of the boundary between Charles and St. Mary's counties.

Scenic River Commissions oversee it in Charles and St. Mary's counties.