iridovirus, any virus belonging to the family Iridoviridae. Iridoviruses possess large enveloped or nonenveloped virions (virus particles) that measure 120–350 nm (1 nm = 10−9 metre) in diameter. The capsid (the protein shell surrounding the viral nucleic acids) is icosahedral and contains linear double-stranded DNA.
Among the genera included in this family are Iridovirus, Chloriridovirus, Lymphocystivirus, Ranavirus, and Megalocytivirus. Type species of the family include invertebrate iridescent virus 6 (Iridovirus), which infects insects; lymphocystis disease virus 1 (Lymphocystivirus), which infects fish; and frog virus 3 (Ranavirus), which infects amphibians.