The National Institute of Environmental Health Sciences (NIEHS) conducts research into the effects of the environment on human disease, as one of the 27 institutes and centers of the National Institutes of Health (NIH). It is located in the Research Triangle Park in North Carolina, and is the only primary division of the NIH located outside of the Washington metropolitan area.

The National Institutes of Health, commonly referred to as NIH, is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late 1880s and is now part of the United States Department of Health and Human Services. Many NIH facilities are located in Bethesda, Maryland, and other nearby suburbs of the Washington metropolitan area, with other primary facilities in the Research Triangle Park in North Carolina and smaller satellite facilities located around the United States. The NIH conducts its own scientific research through the NIH Intramural Research Program (IRP) and provides major biomedical research funding to non-NIH research facilities through its Extramural Research Program.