Valerius Cordus (1515-1544) was a physician born in Erfurt in the state of Hesse (now part of Germany). His father, Euricius Cordus , was also a physician. Cordus obtained a degree in medicine at the University of Wittemberg in 1531. In 1540 he became the first person (at least in Europe) to synthesize ether, a volatile organic liquid which at the time was called "sweet oil of vitriol", by adding sulphuric acid to alcohol. (Paracelsus is sometimes credited instead with this discovery.) He may have learnt the technique from Portuguese travellers who had recently made the first European expeditions to the Middle East.

In 1549, notes from his Wittemberg lectures, entitled Annotations on Dioscorides, were published, based on his own systematic observations of the plants described by the Classical writer Dioscorides.

His De Extractione, printed in 1561, contained the first publication of his technique for synthesizing ether. Historia Stirpium et Sylva was published in the same year.

The Cordia genus of plants of the Boraginaceae family is named after him.