Assunpink Creek is a 22.9-mile-long (36.9 km)[1] tributary of the Delaware River in western New Jersey in the United States.

Flowing westwards, it soon enters the Assunpink Wildlife Management Area, where it has been dammed to form Rising Sun Lake.

Bridegroom Run enters from the north side as the creek turns west and is impounded to form Mercer Lake.

It then passes under Quaker Bridge Road and Interstate 295 before turning southwest and paralleling the Delaware and Raritan Canal.

On January 2, 1777, during the Second Battle of Trenton of the American Revolutionary War, soldiers of the Continental Army and supporting militias, under the direct command of General George Washington, held a defensive line along the south shore of Assunpink Creek south of Trenton, stretching from the mouth of the creek up to Philip's Mill.