Human aging presents an evolutionary paradox: while aging rates remain constant, healthspan and lifespan vary widely. We address this conundrum via salutogenesis-the active production of health-through immune resilience (IR), the capacity to resist disease despite aging and inflammation. Analyzing ~17,500 individuals across lifespan stages and inflammatory challenges, we identified a core salutogenic mechanism: IR centered on TCF7, a conserved transcription factor maintaining T-cell stemness and regenerative potential. IR integrates innate and adaptive immunity to counter three aging and mortality drivers: chronic inflammation (inflammaging), immune aging, and cellular senescence. By mitigating these aging mechanisms, IR confers survival advantages: At age 40, individuals with poor IR face a 9.7-fold higher mortality rate-a risk equivalent to that of 55.5-year-olds with optimal IR-resulting in a 15.5-year gap in survival. Optimal IR preserves youthful immune profiles at any age, enhances vaccine responses, and reduces burdens of cardiovascular disease, Alzheimer's, and serious infections. Two key salutogenic evolutionary themes emerge: first, female-predominant IR, including TCF7, likely reflects evolutionary pressures favoring reproductive success and caregiving; second, midlife (40-70 years) is a critical window where optimal IR reduces mortality by 69%. After age 70, mortality rates converge between resilient and non-resilient groups, reflecting biological limits on longevity extension. TNFα-blockers restore salutogenesis pathways, indicating IR delays aging-related processes rather than altering aging rates. By reframing aging as a salutogenic-pathogenic balance, we establish TCF7-centered IR as central to healthy longevity. Targeted midlife interventions to enhance IR offer actionable strategies to maximize healthspan before biological constraints limit benefits.