Abstract: Provided are methods and compositions for inhibiting viral infections. In some embodiments, the methods include administering to a subject infected with and/or at risk for infection with a virus a composition having a glucosylceramidase inhibitor, a glucosylceramide synthase inhibitor, or any combination thereof via a route and in an amount effective for treating and/or inhibiting the viral infection in the subject. Also provided are methods for inhibiting viral infections of cells, methods for inhibiting endosomal fusion of viruses in cells, and compositions for use in treating and/or inhibiting viral infections of subjects and/or cells.