The Munchkin River is a river that flows through the Munchkin Country of the Land of Oz. It interrupts the path of the Yellow Brick Road near a Poppy Field.
The Scarecrow was briefly stranded on a pole in the middle of the river. He was rescued by a passing Stork. (The Wonderful Wizard of Oz)
In his non-canonical Dorothy of Oz, Roger S. Baum includes a voyage through the Gillikin Country on the Munchkin River on a tugboat named Tugg.