The Safe Drinking Water Act (SDWA), Title XIV of the Public Health Service Act, is the key federal law for protecting public water supplies from harmful contaminants. The SDWA applies to every public water supply systems (PWS) in the United States, which amounts to approximately 87% of all water used in the United States and includes include both public and private municipal water companies, homeowner associations, schools, businesses, campgrounds, and shopping malls. The SDWA authorizes the EPA to set national health-based standards for drinking water to protect against both naturally occurring and man-made contaminants that may be found in drinking water. The EPA, states, and PWSs then work together to make sure that these standards are met. This chapter provides an overview of the Safe Drinking Water Act through a discussion of regulated public water systems, details of the act, drinking water standards, primary and secondary drinking water regulations, and unregulated contaminants. The applications section provides four Illustrative Examples related to the general subject of the Safe Drinking Water Act.