Background.We aimed to characterize the natural history of hepatitis C virus (HCV) reinfection and spontaneous clearance following reinfection (reclearance), including predictors of HCV reclearance. Methods.Data were synthesized from the 9 prospective cohorts of the International Collaboration of Incident Human Immunodeficiency Virus and HCV in Injecting Cohorts study, which evaluated HCV infection outcomes among people who inject drugs. Participants with primary HCV infection were classified as having achieved viral suppression if they had negative results of at least 1 subsequent HCV RNA test. Those with positive results of an HCV RNA test following viral suppression were investigated for reinfection. Viral sequence analysis was used to identify reinfection (defined as detection of heterologous virus with no subsequent detection of the original viral strain). Results.Among 591 participants with acute primary HCV infection, 118 were investigated for reinfection. Twenty-eight participants were reinfected (12.3 cases/100 person-years; 95 confidence interval [CI], 8.5-17.8). Peak HCV RNA level was lower during reinfection than primary infection (P =. 011). The proportion of individuals with reclearance 6 months after reinfection was 52 (95 CI, 33 -73 ). After adjustment for study site, females with the IFNL4 (formerly IFNL3 and IL28B) rs12979860 CC genotype detected were more likely to have reclearance (hazard ratio, 4.16; 95 CI, 1.24-13.94; P =. 021). Conclusions.Sex and IFNL4 genotype are associated with spontaneous clearance after reinfection.