Virophages are double-stranded DNA viruses that share properties with satellite viruses and inhibit or impair the reproduction of the auxiliary virus. As other satellite viruses, virophages depend on the coinfection of their host by another virus, typically a giant virus. In contrast to satellite viruses, virophages encode their own DNA replication proteins and are assumed to depend on the transcription proteins provided by the coinfecting giant virus. The virophage usually jeopardizes the reproduction of the auxiliary virus, a phenomenon that is also known from some satellite viruses, but Zamilon is an apparent exception.
Virophages are classified within the proposed family Lavidaviridae, with the two genera Sputnikvirus and Mavirus. Known virophages include