Abstract: This scoping review examined the influence of hardiness on the health outcomes of military personnel using the U.S. Army's Holistic Health and Fitness framework, which includes mental, physical, sleep, nutritional, and spiritual health domains. Forty-eight studies published between 1990-2025 were analyzed. Most studies focused on mental and physical health, with fewer examining sleep, nutritional, and spiritual health. Findings indicated that lower hardiness levels were associated with adverse health outcomes, often mediated by maladaptive coping strategies. Hardiness also appeared to buffer the effects of stress on mental, physical, and nutritional health. However, most studies were cross-sectional (63%). Research on how hardiness influences underexplored health domains and how it may be enhanced through targeted training is limited. Future studies should use longitudinal and experimental designs to clarify causal pathways and inform potential applications. Such research could pave the way for evidence-based hardiness interventions that support the holistic health of military personnel.