In this Special Issue, 'Vitamin C: from Bench to Bedside', we collected original research papers and comprehensive review articles spanning laboratory-based research, observational studies, and intervention trials. These cover the following key research themes: pharmacokinetics; immune function; epidemiology; cancer research; surgical outcomes; and infection research, specifically pneumonia, sepsis, and COVID-19. Collectively, this Special Issue displays the diverse areas of health and disease in which vitamin C plays important roles and the continuing efforts of researchers to unravel the underlying mechanisms of its biological functions.