Retrovirus, any of a group of viruses that belong to the family retroviridae and that characteristically carry their genetic blueprint in the form of ribonucleic acid (RNA). They have ssRNA as genetic material. It is a type of RNA virus that inserts a copy of its genome into the DNA of a host cell that it invades, thus changing the genome of that cell. It uses a special enzyme called reverse transcriptase to translate its genetic information into DNA.

That DNA can then integrate into the host cell's DNA. Once integrated, the virus can use the host cell's components to make additional viral particles.