Environmental pollution is fundamentally a chemical problem involving the introduction, transformation, transport, persistence, and accumulation of substances in air, water, soil, and biological systems. Industrialization, agricultural intensification, urbanization, transportation, energy production, and increasing consumption of synthetic chemicals have introduced a diverse range of inorganic and organic pollutants into the environment. Conventional pollutants such as sulfur oxides, nitrogen oxides, carbon monoxide, particulate matter, pesticides, petroleum-derived compounds, and heavy metals continue to pose significant environmental challenges, while emerging contaminants including pharmaceuticals, personal care products, endocrine-disrupting chemicals, per- and polyfluoroalkyl substances (PFAS), microplastics, and antimicrobial-resistance-related contaminants have expanded the scope of environmental chemistry. This review examines environmental pollution from a chemistry-centered perspective, emphasizing pollutant classification, sources, chemical properties, transformation processes, transport, persistence, toxicity, and remediation. Particular attention is given to chemical reactions occurring in the atmosphere and aquatic and terrestrial environments, including oxidation, reduction, hydrolysis, photochemical transformation, adsorption, complexation, precipitation, and biodegradation. The review also considers advanced remediation approaches such as adsorption, membrane separation, advanced oxidation processes, photocatalysis, biological treatment, and integrated treatment systems. Current evidence indicates that pollution control requires not only removal of contaminants but also understanding their transformation products and environmental fate. Emerging pollutants present additional challenges because many occur at trace concentrations while remaining chemically persistent or biologically active. Future environmental chemistry research should therefore integrate molecular-level characterization, transformation pathways, toxicity assessment, life-cycle thinking, and sustainable remediation technologies.