Aim: The aim of this chapter is to review the types of groundwater dependent ecosystems (GDEs) that occur across subsurface, terrestrial and aquatic realms. Main concepts covered: GDEs are natural systems that require access to groundwater to maintain their biodiversity and ecosystem processes. Main methods covered: We considers the aspects of the groundwater regime (depth, flux, pressure and quality) needed to sustain GDEs, and threats to their conservation and management. Conclusion/outlook: Limited knowledge of the degree and timing of groundwater dependency of most GDEs, and the pressures of climate change are challenges for the management and conservation of these valuable ecosystems.