Background: CD163, a monocyte- and macrophage-specific scavenger receptor, is shed as soluble CD163 (sCD163) during the proinflammatory response. Here, we assessed the association between plasma sCD163 levels and progression to AIDS and all-cause mortality among individuals infected with human immunodeficiency virus type 1 (HIV). Methods: Plasma sCD163 levels were measured in 933 HIV–infected individuals. Hazard ratios (HRs) with 95% confidence intervals (CIs) associated with mortality were computed by Cox proportional hazards regression. Results: At baseline, 86% were receiving antiretroviral treatment, 73% had plasma a HIV RNA level of <50 copies/mL, and the median CD4+ T-cell count was 503 cells/µL. During 10.5 years of follow-up, 167 (17.9%) died. Plasma sCD163 levels were higher in nonsurvivors than in survivors (4.92 mg/L [interquartile range {IQR}, 3.29–8.65 mg/L] vs 3.16 mg/L [IQR, 2.16–4.64 mg/L]; P = .0001). The cumulative incidence of death increased with increasing plasma sCD163 levels, corresponding to a 6% or 35% increased risk of death for each milligram per liter or quartile increase, respectively, in baseline plasma sCD163 level (adjusted HR, 1.06 [95% CI, 1.03–1.09] and 1.35 [95% CI, 1.13–1.63], respectively). Conclusions: Plasma sCD163 was an independent marker of all-cause mortality in a cohort of HIV–infected individuals, suggesting that monocyte/macrophage activation may play a role in HIV pathogenesis and be a target of intervention.