Substituted arylthiourea compounds of Formula I, and the pharmaceutically acceptable salts of such compounds, useful as antiviral agents, are provided herein. Certain substituted arylthioureas disclosed herein are potent and/or selective inhibitors of viral replication, particularly Hepatitis C virus replication. Pharmaceutical compositions containing one or more substituted arylthiourea compounds and one or more pharmaceutically acceptable carriers, excipients, or diluents are provided herein. Such pharmaceutical compositions may contain a substituted arylthiourea as the only active agent or may contain a combination of a substituted arylthiourea derivative and one or more other pharmaceutically active agents. Methods of treating Hepatitis C viral infections in mammals are also provided herein.