Intermittent Spring, Rhythmic spring in Swift Creek canyon near Afton, Wyoming, US.

Intermittent Spring, also called Periodic Spring, flows from a cavern in Swift Creek canyon in the Star Valley near Afton, Wyoming. Groundwater fills a narrow tube; when it pours over the tube's high point, a siphon effect draws water out until air rushes in and breaks the flow. The spring sits at 2,244 metres on a mountainside about 7 km east of Afton.

A local logger discovered this spring during early exploration of Lincoln County and documented its unusual water flow pattern. The discovery later drew scientific attention as researchers studied the phenomenon of rhythmic water discharge in geological systems.

The spring's discovery is credited to the great-great-grandfather of Rulon Gardner, the Afton-area wrestler who won Olympic gold in Greco-Roman wrestling in 2000. Gardner recounts that his ancestor was up in the canyon logging when he found a small spot for fresh water and noticed it ran, then stopped.

The spring is reachable via a maintained hiking trail from Swift Creek Road that leads directly to viewing areas. The best time to visit is during warmer months when the ground is accessible and you can clearly watch the water cycle through its active and inactive phases.

The spring sits at 2,244 metres in Swift Creek canyon, about 7 km east of Afton, and the surrounding slopes rise to 2,848 metres within roughly a kilometre. Its discovery is credited to the great-great-grandfather of wrestler Rulon Gardner, who came upon it while logging and fetching fresh water.