Book excerpt: The Ganges Basin is a part of the Ganges-Brahmaputra-Meghna (GBM) River Basin and is one of the most populated (600 million) river basins in the world. This study focuses on the Eastern Ganges Basin (EGB) and covers India (Bihar, Jharkhand and West Bengal), Bangladesh and the Nepal Terai. Poverty is acute in the EGB, where household incomes are low, food security is not assured and devastating floods (and also water shortages) occur too often. The EGB is underlain by one of the most prolific aquifers in the world. Yet, farmers struggle to cope with dry spells and droughts because of their inability to access groundwater. Huge untapped groundwater, surplus surface water, and enormous plains and fertile lands highlight the requirement of proper planning for groundwater management and governance to reduce poverty and assure food security. The aim of this report is to assist planners/policymakers in the planning and management of groundwater resources in the EGB. This report mainly discusses about hydrogeology, groundwater potential and challenges, and groundwater quality issues in the EGB. Moreover, it is an attempt to form a base for future work related to groundwater development, management and modeling in this basin.