What is the name of the first virus discovered?

The first virus discovered was tobacco mosaic virus. It infects tobacco and other plants, producing the mottled leaf pattern known as mosaic disease.

The discovery emerged in the late nineteenth century. Adolf Mayer showed in 1886 that diseased tobacco sap could transmit the illness. In 1892, Dmitri Ivanovsky found that the infectious agent passed through filters designed to retain bacteria. Martinus Beijerinck later repeated the work and concluded that the agent was something fundamentally different from bacteria, helping establish the modern concept of a virus.

Tobacco mosaic virus became a landmark in biology because it could be purified and crystallized. Wendell Stanley crystallized it in 1935, demonstrating that a virus could retain infectivity after crystallization. Later research showed that TMV consists of a single-stranded RNA genome enclosed in a helical protein coat.

A common mix-up is to name a human virus such as influenza or poliovirus. Those viruses were discovered later; TMV was the first recognized example of a filterable infectious agent now classified as a virus.