Groundwater has been extensively exploited worldwide but is now confronted by a variety of problems, including groundwater depletion and contamination, that threaten its sustainable use as a clean water source. Groundwater is one of the major sources of water for domestic, agricultural and industrial uses, and provides 13% of the total annual water supply in Korea. Annual groundwater use has continuously increased from 2.57 billion m3 in 1994 to 3.72 billion m3 in 2007, of which 48.1% was consumed for domestic purposes. However, due to imprudent groundwater development and inappropriate management, Korea has confronted some critical groundwater problems, including extensive water level decline and quality deterioration caused by petroleum hydrocarbons and chlorinated solvents. Among 193 national groundwater deep-monitoring wells nationwide, 62% showed decreasing water levels over the period 2004–2008. Soil and groundwater contamination by petroleum hydrocarbons was detected at a great number of military bases and public facilities, which drew national attention and complaints. The presence of high levels of radionuclides such as uranium and radon in groundwater has awakened controversy on their health effects. Increasing outbreaks of massive gastroenteritis were attributed to noroviruses in contaminated groundwater, and raised public health concerns. In addition, chlorinated solvents, especially trichloroethylene (TCE), have been frequently found in urban and industrial groundwaters, further adding to the burdens of environmental authorities. Consequently, these groundwater-related environmental issues have forced the Korean government and relevant authorities to urgently devise mitigation plans to secure a sustainable future use of groundwater resources. This paper provides details of the groundwater issues and implications for appropriate development and management.