Mavirus is a genus of double stranded DNA virus that can infect the marine phagotrophic flagellate Cafeteria roenbergensis, but only in the presence of the giant CroV virus (Cafeteria roenbergensis).

Mavirus can integrate into the genome of cells of C. roenbergensis, and thereby confer immunity to the population [3] The name is derived from Maverick virus.

The virophage was discovered by Matthias G. Fischer of the University of British Columbia while he was working on Cafeteria roenbergensis virus as part of his PhD.

[2] The genome encodes a retroviral integrase, an adenosine triphosphatase (ATPase), a cysteine protease and a protein primed DNA polymerase B.

[citation needed] Mavirus is a genus in the family Lavidaviridae, which has been established by the International Committee on Taxonomy of Viruses in 2016.