This study demonstrates the effectiveness of a monoclonal antibody cocktail (ZMapp™) in treating advanced Ebola virus (EBOV) disease in nonhuman primates (NHPs). ZMapp™, derived from two previous antibody cocktails (MB-003 and ZMAb), was found to be 100% effective in rescuing rhesus macaques when treatment was initiated up to 5 days post-challenge. High fever, viremia, and abnormalities in blood counts and chemistry were evident in many animals before ZMapp™ intervention. Advanced disease, characterized by elevated liver enzymes, mucosal hemorrhages, and generalized petechia, could be reversed, leading to full recovery. ELISA and neutralizing antibody assays indicate that ZMapp™ is cross-reactive with the Guinean variant of EBOV. The results suggest that ZMapp™ currently exceeds all previous descriptions of efficacy with other therapeutics and warrant further development for clinical use.This study demonstrates the effectiveness of a monoclonal antibody cocktail (ZMapp™) in treating advanced Ebola virus (EBOV) disease in nonhuman primates (NHPs). ZMapp™, derived from two previous antibody cocktails (MB-003 and ZMAb), was found to be 100% effective in rescuing rhesus macaques when treatment was initiated up to 5 days post-challenge. High fever, viremia, and abnormalities in blood counts and chemistry were evident in many animals before ZMapp™ intervention. Advanced disease, characterized by elevated liver enzymes, mucosal hemorrhages, and generalized petechia, could be reversed, leading to full recovery. ELISA and neutralizing antibody assays indicate that ZMapp™ is cross-reactive with the Guinean variant of EBOV. The results suggest that ZMapp™ currently exceeds all previous descriptions of efficacy with other therapeutics and warrant further development for clinical use.