Bijou Geyser is a small but remarkably persistent geyser in Yellowstone National Park’s Upper Geyser Basin, where many geothermal features cluster on a broad thermal plain. Instead of erupting at distinct intervals, it usually plays almost continuously, sending up a fountain about 15 feet high and sometimes shifting into a steam phase. Part of the Giant Group on the Giant Platform, Bijou is linked underground with Giant Geyser and Grotto Geyser, and its activity changes with conditions in that larger hydrothermal system. Because it responds to neighboring geysers and recovery cycles after Giant erupts, Bijou helps reveal Yellowstone’s geothermal features as an interconnected, changing underground network.