Gases released from a volcano provide unique insights into a volcano’s interior and are critical for volcano monitoring. The amount of gas released from a volcano is related to the quantity of magma in the crust. The composition of the gases allows scientists to distinguish magmatic from hydrothermal gases and to estimate the depth of degassing magma. These clues into a volcano’s interior are key factors used to help forecast the timing and explosivity of impending eruptions. Alaska is home to 52 historically active volcanoes, over half of which are persistently degassing. This talk will explore the ways in which volcanic gases are used to monitor volcanoes and forecast eruptions, illustrate the challenges in collecting and interpreting these measurements, and provide examples of how these results have been used to understand the plumbing systems of Alaska’s volcanoes.