Vitamin C, a ubiquitous water-soluble vitamin, has been demonstrated to have several biological activities, including the promotion of collagen production, enhancement of immunity, facilitation of iron absorption, and improvement of fat metabolism. Thus, it has a multitude of applications in the medical field, such as whitening, antioxidation, and the prevention of a wide range of diseases. Conversely, its lack of stability and low permeability limit its applicability. This review presents a summary of the physicochemical properties, delivery strategies, and biological activities of vitamin C. Additionally, this review provides an overview of its preventive and therapeutic effects on diseases such as cataracts, tumors, and cardiovascular conditions. Finally, this review explores the prospective applications of vitamin C as a pharmaceutical agent. A variety of vitamin C derivatives and delivery systems have been developed to overcome the instability and low permeability of vitamin C. However, several challenges persist, including the uncertain efficacy of derivatives and the complexities associated with the implementation of delivery systems. It is anticipated that future advancements will facilitate the development of delivery forms and the utilization of vitamin C in novel applications.