The Lackawaxen River is a 31.3-mile-long (50.4 km) tributary of the Delaware River in northeastern Pennsylvania in the United States. The river flows through a largely rural area in the northern Pocono Mountains, draining an area of approximately 598 square miles (1,550 km2). The river is a popular destination for canoeing and recreational fly fishing for trout. It was reportedly where the American author Zane Grey first learned to fly fish. Lackawaxen is Lenape for "swift waters".