Abstract: A model of a multidomain complex is constructed using molecular modeling methods to explain the mechanism of the inhibitory effect of favipiravir on RNA-dependent RNA polymerase (RdRp) of the SARS-CoV-2 coronavirus. As the initial atomic coordinates, we use cryoelectron microscopy data for the apo form of RdRp of the SARS-CoV-2 virus and data on the structure of RdRp of the hepatitis C virus. After appropriate substitutions, an RdRp complex containing RNA chains and a potential enzyme inhibitor, favipiravir in the form of ribosatriphosphate, are constructed. The structure of the complex in aqueous shells, which includes more than 100 000 atoms, is optimized by molecular dynamics methods. Analysis of the active site with the incorporated favipiravir molecule makes it possible to explain the chemical reaction of the enzyme with the inhibitor.