The scientists were successful in identifying the Hepatitis C virus which causes cirrhosis and liver cancer.
The 2020 Nobel Prize for Medicine winners went to scientists Harvey Alter, Charles Rice, and Briton Michael Houghton.
Their Hepatitis C discovery meant there was now a chance of eradicating the virus completely, the award-giving body said.
"Prior to their work, the discovery of the Hepatitis A and B viruses had been critical steps forward," the Nobel Assembly at Sweden's Karolinska Institute said in a statement on awarding the prize of 10 million Swedish crowns ($1.1 million).
"The discovery of the Hepatitis C virus revealed the cause of the remaining cases of chronic hepatitis and made possible blood tests and new medicines that have saved millions of lives."
While the Nobel awards will go ahead as planned this year, they have been overshadowed by the coronavirus pandemic.
The Nobel Foundation has canceled the traditional banquet, which forms the center-piece of the celebrations in December, and will hand out the medals and diplomas in a televised event rather than live in Stockholm.