Glaciers are masses of land ice that form where snow accumulates, compacts, and transforms into ice over time. They range in size from small cirque glaciers located in high mountain environments to large valley glaciers extending through entire mountain systems. Changes in glaciers are an indicator of climate change as their mass balance (gains versus losses) directly reflects global warming. Glacier changes over time impact the global sea level and the regional water cycle and may increase local hazard risks. Geodesy provides time series data of ice volume changes inferred from satellite altimetry observations, flow velocities inferred from interferometric SAR, and mass changes inferred from satellite gravimetry (although limited to large glaciers). This information is essential for studying mass balance, identifying contributors to sea level change, monitoring availability of fresh water, predicting/mitigating risks associated with ice melting, and informing regional and global climate agreements and adaptation strategies. The following geodetic products are key to realising, monitoring and applying this Essential Geodetic Variable: