Blue Star Spring

Overview

Blue Star Spring is a compact, intensely blue hot spring in the Upper Geyser Basin, a short stroll on the boardwalks behind Old Faithful. Its pale sinter rim and narrow runoff channel give a subtle star‑like outline, and the water stays so hot that few thermophiles grow, keeping that jewel‑tone clarity. Average temperature hovers around 190°F, and while it’s primarily a quiet hot spring, it has been known to produce rare low splashes and steam‑bubble “flames.”

What You’ll See

Expect a small, crystalline pool with striking blue color and a defined rim, draining toward the Firehole River. On calm, low‑steam moments, you can peer straight down into its vent. Some visitors notice bones from a bison calf that fell in decades ago—an eerie reminder of how unforgiving these features are. The “star” shape is subtle today, but the color alone makes it worth a pause.

Geology in Plain English

Hot springs like this don’t erupt regularly: hot water rises, cools, and sinks without building the pressure a geyser needs. Yellowstone’s hydrothermal areas are living systems—rims, runoff, and behavior shift over time—so the look of Blue Star Spring can evolve from year to year.

Getting There & Logistics

Park at the main Old Faithful/Upper Geyser Basin lots and follow the easy boardwalk loop; you’ll pass several features, including this one, in quick succession. There are no toilets or picnic tables on the boardwalk—use facilities in the Old Faithful village area when open. Pets aren’t allowed on the boardwalks.

Safety

Stay on the boardwalks. The crust is thin in places and the water can cause severe burns. Supervise kids and never toss objects into the pool—the spring was once cleaned of trash, and it’s not a souvenir pit.

Best Time to Visit

Early morning is the sweet spot: fewer people spill over from Old Faithful, and with less steam the colors pop. Mid‑mornings, especially on weekends, draw the biggest crowds. If it’s steamy, wait for a breeze to clear the view before you snap photos.