This chapter titled �Sources of Water Contamination by Heavy Metals� provides an extensive discussion of the various sources of heavy metals in water bodies. Heavy metals are defined and their properties and uses are outlined. The chapter examines the different sources of heavy metals, including natural, anthropogenic, and from diverse sources such as waste materials and industrial processes. The sources, characteristics, uses, and impacts of individual heavy metals including arsenic, nickel, zinc, lead, mercury, copper, chromium, and cadmium are also discussed in detail. Furthermore, the chapter evaluates the different indexing approaches for heavy metal pollution including the heavy metal pollution index (HPI), the contamination index (CI), the evaluation index of heavy metals (HEI), and the heavy metal index (HMI). The analytical methods for heavy metal detection are also discussed, including broad categories such as spectroscopic detection, electrochemical detection, and optical methods of detection. This chapter will be useful to researchers and professionals in the fields of environmental science, chemistry, engineering, and water resources management who are interested in understanding the sources and impacts of heavy metal contamination in water bodies. The information provided in this chapter will also be useful for the development of effective strategies for the prevention and mitigation of heavy metal pollution in water bodies. © 2024 selection and editorial matter, Juhana Jaafar, Asad A. Zaidi and Muhammad Nihal Naseer.