Temin, Howard Martin (1934-1994) was an American molecular biologist and virologist who discovered that genetic information in ribonucleic acid (RNA) can be copied into deoxyribonucleic acid (DNA). For this he shared the 1975 Nobel Prize in physiology or medicine with fellow Americans David Baltimore and Renato Dulbecco .

Temin was born in Philadelphia and became interested in science at an early age. As a teenager, he was a special student at summer sessions at the Jackson Laboratory at Bar Harbor, Maine. He majored and minored in biology at Swarthmore College in Pennsylvania, where he received a bachelor's degree in 1955. He was admitted to the graduate program at the California Institute of Technology (Caltech), majoring in animal virology. There he studied under Dulbecco, and after earning a Ph.D. degree in 1959, he worked with Dulbecco for another year. In 1960, he accepted a position at the McArdle Laboratory for Cancer Research at the University of Wisconsin-Madison, where he remained for the rest of his career.

While at Caltech, Temin had begun studying the Rous sarcoma virus (RSV), which was one of the first viruses known to cause tumors. He continued this research at Wisconsin and in 1965 presented his theory that some viruses cause cancer through information transfer from RNA to DNA. Until then, the prevailing belief was that genetic information could pass only from DNA to RNA, and Temin's findings were greeted mainly with skepticism. However, Temin and Baltimore, working independently, identified an enzyme called reverse transcriptase. That enzyme synthesizes cell DNA by turning RNA into double-stranded DNA and allowing it to enter the host cell. There it directs production of the next generation of the virus and is inherited by future cell generations. Viruses containing reverse transcriptase are known as retroviruses, because they reverse the usual process of transferring genetic information from DNA to RNA. This discovery has been especially valuable in research on AIDS, which is caused by a retrovirus. It has also been useful in cloning, genetic engineering, and cancer research.