Heavy metal contamination in aquatic ecosystems poses serious environmental risks due to their persistence, toxicity, and bioaccumulation. This review outlines global regulatory benchmarks (WHO and USEPA) and identifies major sources such as industry, agriculture, wastewater, mining, and natural processes. Metals accumulate in sediments and organisms, causing physiological harm to aquatic life and disrupting food webs through bioaccumulation and biomagnification. Contamination also degrades water quality by altering pH, turbidity, and oxygen levels. Detection methods include AAS, ICP-MS, biosensors, and bioindicators. Remediation strategies involve physicochemical treatments, bioremediation, sediment management, constructed wetlands, and emerging technologies like nanotech and electrochemical processes. Integrated monitoring and mitigation are essential to restore aquatic ecosystem health.