Environmental pollution has intensified due to rapid industrialization, urbanization, mining, and agricultural activities, leading to the continuous accumulation of toxic contaminants in water, soil, and air. These pollutants include heavy metals, pesticides, dyes, pharmaceuticals, and emerging organic compounds that persist in the environment and pose serious risks to ecosystems and human health. Conventional remediation methods are often inefficient, expensive, and generate secondary waste, limiting their large-scale applicability. In this context, functional nanomaterials offer advanced and sustainable solutions due to their high surface area, enhanced reactivity, and multifunctional properties that enable efficient pollutant removal. Their unique nanoscale features allow improved interaction with contaminants, resulting in higher adsorption capacity and faster degradation rates compared to traditional materials. Additionally, these materials can be engineered for specific applications, making them highly versatile for environmental cleanup. This review summarizes their synthesis, characterization, mechanisms, applications, safety issues, and future prospects for sustainable environmental remediation.