Phytochemicals represent a privileged reservoir of structurally diverse chemical scaffolds that have historically served as templates for pharmaceutical innovation. Spanning alkaloids, terpenoids, polyphenols, and polyketides, these natural products exhibit exceptional molecular complexity and occupy pharmacologically relevant chemical space that remains underexplored by synthetic libraries. This review examines phytochemicals through the lens of contemporary drug discovery, focusing on their utility as lead compounds rather than botanical extracts. We discuss systematic approaches to lead identification, including target-based screening, phenotypic assays, and computational methods that leverage natural product databases for virtual screening. Key optimization strategies—including semi-synthesis, scaffold hopping, and fragment-based elaboration—are analyzed to address common limitations such as poor bioavailability, metabolic instability, and unfavorable physicochemical properties. Therapeutic applications span oncology, neurodegenerative disorders, metabolic diseases, and infectious diseases, with emphasis on mechanistic pharmacology and validated molecular targets. Critical translational barriers including supply chain sustainability, stereochemical complexity, and regulatory frameworks are evaluated alongside emerging solutions such as biosynthetic pathway engineering and AI-assisted retrosynthetic planning. The integration of multi-omics platforms, structure-based design, and patient stratification strategies promises to accelerate the clinical translation of phytochemical-derived therapeutics. This perspective underscores the enduring relevance of natural product chemistry in expanding druggable target space and delivering first-in-class pharmaceutical agents.