Abstract:    Phytochemicals are naturally occurring bioactive compounds found in plants that have emerged as promising agents in the prevention and management of chronic diseases. As interest in natural therapeutics grows, driven by concerns about the limitations of conventional medicine, phytochemicals offer a compelling alternative due to their wide range of biological activities and favourable safety profiles. This review provides a comprehensive overview of the major classes of phytochemicals, including flavonoids, carotenoids, alkaloids, terpenoids, and others, along with their sources and associated health benefits. The mechanisms by which these compounds exert therapeutic effects—such as antioxidant activity, anti-inflammatory action, gene modulation, and interaction with cellular signalling pathways—are explored in detail. Additionally, the review highlights the role of phytochemicals in combating chronic diseases such as cardiovascular disorders, cancer, diabetes, and neurodegenerative conditions. Despite their potential, challenges remain in translating phytochemical research into clinical practice, including issues related to bioavailability, standardization, and regulatory frameworks. Addressing these barriers through advanced research and innovation is critical to fully harness the therapeutic potential of phytochemicals in modern medicine.