Cryovolcanism is a volcanic phenomenon that occurs in environments with extremely low temperature. There, instead of molten silicates, cryovolcanoes erupt liquid water, methane, ammonia, or sulfur dioxide onto the icy surface of a planet or satellite. It has been observed on several satellites of the outer Solar System. In particular, active cryovolcanism has been discovered at the surface of Io, Jupiter’s innermost Galilean satellite, and on Enceladus, one of Saturn’s satellites. Traces of cryovolcanism are also found on Titan and Triton. Apart from Io’s volcanoes from which sulfur dioxide (SO2) is outgassed, cryovolcanism generally erupts water (H2O), methane (CH4), and ammonia (NH3). Cryovolcanism could also be present on other outer satellites and trans-Neptunian objects.