The Gillikin River is the longest river in the Gillikin Country of the Land of Oz, having its source in the Gillikin Mountains near Up Town. It flows west past the home of the Scooters before draining into the Inland Sea close to the border with the Winkie Country. Tributaries include the Little Gillikin River and Camouflage Creek. Another, shorter river starts in the Hidden Valley, forms part of the border between the Gillikin and Winkie Countries, and flows into the southern end of the Inland Sea.
In the surviving chapters of Jack Snow's original version for The Shaggy Man of Oz, the story has a group of characters (including the Shaggy Man, Dorothy, and Ozma) exploring the Gillikin River on a boat called The Ozma. They enter the face of a cliff and discover a cavern inhabited by the Crystal People, a race of sentient stalactites and stalagmites. Underground springs are the source of the river.
In The Ozmapolitan of Oz, Melody the River Princess, a fairy whose domain is the Winkie River, says one of her three sisters inhabits the Gillikin River.