Starch, a naturally occurring polysaccharide, plays a vital role in food, pharmaceutical, textile, and bio plastic industries due to its renewable, biodegradable, and versatile properties. Traditionally sourced from crops like corn, potato, and wheat, there is a growing interest in exploring non-conventional sources of starch such as banana, jackfruit seed, water chestnut, sago palm, and underutilized legumes and tubers. These alternative sources offer unique physicochemical characteristics, making them potential candidates for functional food formulations and novel industrial applications. The molecular structure of starch—composed of amylose and amylopectin significantly influences its functional properties including gelatinization, retrogradation, solubility, and digestibility. Advances in characterization techniques have allowed for deeper insights into starch granule morphology, crystallinity, and enzymatic resistance. Furthermore, chemical and physical modifications are employed to enhance starch performance in targeted applications, including drug delivery systems and sustainable packaging. This review aims to provide a holistic understanding of starch, covering its diverse sources, structural complexity, functional behavior, and current trends in modification. It also highlights the emerging prospects of starch in nanotechnology, biomedical engineering, and climate-resilient agriculture, underlining its future significance in replacing synthetic polymers and supporting circular bioeconomy models.