Reverse transcriptase is an enzyme that generates complementary DNA from an RNA template, in contrast to the usual information flow from DNA to RNA. It was discovered in Rous sarcoma virus and murine leukaemia virus, two retroviruses, by Howard Temin and David Baltimore, working independently in 1970, for which the two shared the Nobel Prize in Physiology or Medicine.

Reverse transcription is essential for the replication of retroviruses, allowing them to integrate into the host genome as a provirus. The enzyme is a target for reverse-transcriptase inhibitors, a major class of anti-HIV drugs. Reverse transcription is also used by Hepadnaviridae and Caulimoviridae, DNA viruses that replicate via an RNA intermediate, such as hepatitis B. The process is important in the movement of retrotransposons, a type of mobile genetic element, and in the extension of chromosome ends in eukaryotic genomes. The enzyme is widely used in the laboratory for molecular cloning, RNA sequencing, polymerase chain reaction and genome analysis.