A global inventory of groundwater use for irrigation is presented, showing that 38% of the 301 million hectares of irrigated area is equipped with groundwater. Total groundwater use for irrigation is estimated at 545 km³ yr⁻¹, or 43% of total irrigation water use of 1277 km³ yr⁻¹. The largest areas equipped for groundwater irrigation are in India (39 million ha), China (19 million ha), and the USA (17 million ha). Groundwater use in irrigation is increasing both in absolute terms and as a percentage of total irrigation, leading to over-extraction in some regions. Despite uncertainties in statistical data, the inventory provides a comprehensive dataset for 15,038 administrative units, including statistics on groundwater, surface water, and non-conventional sources. The inventory uses data from national census reports and the FAO-AQUASTAT library, and links these to the Global Crop Water Model (GCWM) to estimate consumptive water use. The data is available online and includes detailed country-specific information. The study highlights the importance of groundwater in irrigation, particularly in semi-arid and arid regions, and the need for careful interpretation of the data due to uncertainties in statistical sources. The inventory also shows that groundwater use varies significantly by region and country, with some areas relying heavily on groundwater while others use surface water. The study emphasizes the need for consistent definitions and transparent assumptions in global water resource assessments to avoid additional uncertainties. The results indicate that groundwater is a critical resource for irrigation, but its overuse can lead to depletion and environmental impacts. The study also discusses the limitations of the data and methodology, including the difficulty in accurately determining groundwater use due to the complexity of hydrological processes and the variability in irrigation practices across different regions. The findings highlight the importance of managing groundwater resources sustainably to ensure long-term agricultural productivity and water security.A global inventory of groundwater use for irrigation is presented, showing that 38% of the 301 million hectares of irrigated area is equipped with groundwater. Total groundwater use for irrigation is estimated at 545 km³ yr⁻¹, or 43% of total irrigation water use of 1277 km³ yr⁻¹. The largest areas equipped for groundwater irrigation are in India (39 million ha), China (19 million ha), and the USA (17 million ha). Groundwater use in irrigation is increasing both in absolute terms and as a percentage of total irrigation, leading to over-extraction in some regions. Despite uncertainties in statistical data, the inventory provides a comprehensive dataset for 15,038 administrative units, including statistics on groundwater, surface water, and non-conventional sources. The inventory uses data from national census reports and the FAO-AQUASTAT library, and links these to the Global Crop Water Model (GCWM) to estimate consumptive water use. The data is available online and includes detailed country-specific information. The study highlights the importance of groundwater in irrigation, particularly in semi-arid and arid regions, and the need for careful interpretation of the data due to uncertainties in statistical sources. The inventory also shows that groundwater use varies significantly by region and country, with some areas relying heavily on groundwater while others use surface water. The study emphasizes the need for consistent definitions and transparent assumptions in global water resource assessments to avoid additional uncertainties. The results indicate that groundwater is a critical resource for irrigation, but its overuse can lead to depletion and environmental impacts. The study also discusses the limitations of the data and methodology, including the difficulty in accurately determining groundwater use due to the complexity of hydrological processes and the variability in irrigation practices across different regions. The findings highlight the importance of managing groundwater resources sustainably to ensure long-term agricultural productivity and water security.