The 21st century presents a profound paradox of progress: global advances in medicine and public health have propelled life expectancy to unprecedented heights, yet this triumph is shadowed by a rising tide of age-related chronic diseases. The central challenge is not merely adding years to life, but adding healthy, functional life to years. This gap between lifespan (total years lived) and healthspan (years lived in good health) is driven largely by the high prevalence and complex interplay of multiple chronic conditions, known as multimorbidity. The economic and social burden of aging stems disproportionately from periods of severe illness and functional decline, often concentrated in later life. In response, the World Health Organization has championed a paradigm shift towards "healthy aging," defined as the process of developing and maintaining the functional ability that enables well-being in older age. This refocuses the goal from disease treatment to the optimization of intrinsic capacity—an individual's composite physical and mental resources—and the creation of supportive environments. Therefore, a successful strategy for healthy aging must integrate foundational, population-level interventions across the life course with innovative, personalized biomedical approaches, with emerging gerotherapeutics representing a promising frontier for fundamentally extending healthspan.