While many diseases of aging have been linked to the immunological system, immune metrics with which to identify the most at-risk individuals are lacking. We studied the blood immunome of 1001 individuals aged 8-96 and developed a deep learning method based on patterns of systemic age-related inflammation. The resulting inflammatory clock of aging (iAge) tracked with multiple morbidities, immunosenescence, frailty and cardiovascular aging. We demonstrate that iAge is associated with exceptional longevity in a separate cohort of centenarians. The strongest contributor to this metric was the chemokine CXCL9, which was involved in cardiac aging, adverse cardiac remodeling, and decreased vascular function.Furthermore, aging endothelial cells in human and mice show loss of function, indicators of early cellular senescence and hallmark phenotypes of arterial stiffness, all of which are reversed by silencing CXCL9. In conclusion, we identify a key role of CXCL9 in age-related systemic chronic inflammation and derive a novel metric for age-related multimorbidity that can also be used for early detection of age-related clinical phenotypes.