Henry Cavendish, a brilliant recluse, is credited with its discovery for communicating his work in 1766 to the Royal Society in England with an inflammable gas produced by the action of acids on metal. Although others had worked on it previously, Cavendish was the first to systematically investigate its properties, although it was actually named "hydrogen" 20 years later by the French chemist Lavoisier. Cavendish discovered that burning this gas in the air produced water, which finally ended the Greek concept of immutable elements (earth, air, fire, water). During his experiments with air, he also isolated what later became known as the element argon, but because of his reclusivity, it took a century before his experiment could be followed up. Cavendish's most famous experiment (now known as the "Cavendish Experiment") was his determination of the weight of the Earth.
Asimov's Biographical Encyclopedia of Science and Technology, I. Asimov, pg. 140, 1964.
It would be Henry Cavendish, but the name came from Lavoiser.
Henry Cavendish discovered hydrogen.
Henry Cavendish. He was a British natural philosopher, scientist, and an important experimental and theoretical chemist and physicist. He called Hydrogen 'inflammable air' and also had an experiment to weigh the earth