间歇泉（英语：Geyser）是温泉的一种，因为地下水变成蒸气而间歇地喷出而形成。

间歇泉的英语Geyser是取自Geysir，冰岛语是「喷出」的意思，英国人登陆冰岛后第一次看到间歇泉，因此英语的Geyser语源就是来自冰岛文Geysir。

A geyser (US /ˈɡaɪzər/; UK /ˈɡiːzə/ or /ˈɡaɪzə/) is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by steam.

The formation of geysers is due to particular hydrogeological conditions, which exist in only a few places on Earth, so they are a fairly rare phenomenon. Generally all geyser field sites are located near active volcanic areas, and the geyser effect is due to the proximity of magma. Generally, surface water works its way down to an average depth of around 2,000 metres (6,600 ft) where it contacts hot rocks. The resultant boiling of the pressurized water results in the geyser effect of hot water and steam spraying out of the geyser's surface vent (a hydrothermal explosion).