BACKGROUND AND AIMS: The efficacy and safety of glecaprevir/pibrentasvir (G/P) for patients infected with hepatitis C virus (HCV) have only been investigated in clinical trials, with no real-world data currently available. The aim of our study was to investigate the effectiveness and safety of G/P in a real-world setting. METHODS: All patients with HCV consecutively starting G/P between October 2017 and January 2018 within the NAVIGATORE-Lombardia Network were analyzed. G/P was administered according to drug label (8, 12 or 16 weeks). Fibrosis was staged either histologically or by liver stiffness measurement. Sustained virological response (SVR) was defined as undetectable HCV-RNA 12 weeks after the end of treatment. RESULTS: A total of 723 patients (50% males) were treated with G/P, 89% for 8 weeks. The median age of our cohort was 58 years, with a median body mass index of 23.9 kg/m(2), and median liver stiffness measurement of 6.1 kPa; 84% were F0-2 and 16% were interferon-experienced. Median HCV-RNA was 1,102,600 IU/ml, and 49% of patients had HCV genotype 1 (32% 1b), 28% genotype 2, 10% genotype 3 and 13% genotype 4. The median estimated glomerular filtration rate was 90.2 ml/min, platelet count 209x10(3)/mm(3) and albumin 4.3 g/dl. The SVR rates were 94% in intention-to-treat and 99.3% in per protocol analysis (8-week vs. 12 or 16-week: 99.2% vs. 100%). Five patients failed therapy because of post-treatment relapse; a post-treatment NS5A resistance-associated substitution was detected in 1 case. SVR rates were lower in males (p = 0.002) and in HCV genotype-3 (p = 0.046) patients treated for 8 weeks, but independent of treatment duration, fibrosis stage, baseline HCV-RNA, HIV co-infection, chronic kidney disease stage and viral kinetics. Mild adverse events were reported in 8.3% of the patients, and 0.7% of them prematurely withdrew treatment. Three patients died of drug-unrelated causes. CONCLUSIONS: In a large real-world cohort of Italian patients, we confirmed the excellent effectiveness and safety of G/P administered for 8, 12 or 16 weeks. LAY SUMMARY: A large number of patients with hepatitis C virus have been treated with glecaprevir/pibrentasvir (G/P) within the NAVIGATORE-Lombardia Network, in Italy. This is the first real-world study evaluating effectiveness and safety of G/P in patients with hepatitis C virus treated according to international recommendations. This study demonstrated excellent effectiveness (with sustained virological response rates of 99.3%) and safety profiles.