Jet Geyser, Cone-type geyser in Lower Geyser Basin, Yellowstone National Park, United States

Jet Geyser is a cone-type geyser in the Lower Geyser Basin of Yellowstone National Park, part of the Fountain Group with Fountain Geyser, Morning Geyser, Red Spouter and Silex Spring. It sits beside a park road and a boardwalk. At least five vents throw water and steam vertically, at an angle and almost horizontally for about 0.25 to 1 minute; the central vent usually reaches about 20 feet (6.1 m).

Jet Geyser sits in the Fountain Group of the Lower Geyser Basin, alongside Fountain Geyser, Morning Geyser, Red Spouter and Silex Spring. Its eruption rhythm is tied to Fountain Geyser: Jet erupts every 7 to 30 minutes, more often as a Fountain eruption approaches, and every 1 to 4 minutes during most Fountain eruptions. After Fountain stops, Jet usually stops too, and it often begins a new series midway through a Fountain interval.

Jet Geyser sits beside a park road and a boardwalk in the Fountain Group, so visitors watch its eruptions at close range. Its cone has at least five vents that spray vertically, at an angle and almost horizontally, the central one reaching about 20 feet (6.1 m).

Visitors can watch eruptions from designated wooden boardwalks while maintaining a safe distance since the expelled water reaches very high temperatures. The best viewing conditions typically occur during early morning hours or in clear weather.

Jet's eruptions are not random: they are paced by Fountain Geyser nearby. Jet erupts every 7 to 30 minutes, quickening to every 1 to 4 minutes during most Fountain eruptions, and usually stops once Fountain quits. It often begins a new series roughly midway through a Fountain interval.