Four drugs were trialled on patients in the Democratic Republic of Congo, where there is a major outbreak of the virus.
More than 90% of infected people can survive if treated early with the most effective drugs, the research showed.
The drugs will now be used to treat all patients with the disease in DR Congo, according to health officials.
The US National Institute of Allergy and Infectious Diseases (NIAID), which co-sponsored the trial, said the results are “very good news” for the fight against Ebola.
The drugs, named REGN-EB3 and mAb114, work by attacking the Ebola virus with antibodies, neutralising its impact on human cells.
They are the “first drugs that, in a scientifically sound study, have clearly shown a significant diminution in mortality” for Ebola patients, said Dr Anthony Fauci, director of NIAID.
REGN-EB3 and mAb114 were developed using antibodies harvested from survivors of Ebola, which has killed more than 1,800 people in DR Congo in the past year.
Two other treatments, called ZMapp and Remdesivir, have been dropped from trials as they were found to be less effective.
Hailing the success of the study, Jeremy Farrar, director of the Wellcome Trust global health charity, said the treatments would “undoubtedly save lives”.
The findings, Mr Farrar said, indicate scientists are getting closer to turning Ebola into a “preventable and treatable” disease
It is hoped that the effectiveness of the drugs, made by US-based pharmaceutical firms, will make patients feel “more comfortable about seeking care early”, said Dr Fauci.