Where and how was hydrogen discovered?

Answer 1

Scientists had been producing hydrogen for years before it was recognized as an element. Written records indicate that Robert Boyle produced hydrogen gas as early as 1671 while experimenting with iron and acids. Hydrogen was first recognized as a distinct element by Henry Cavendish in 1766.

The answers to when and who are probably lost in the mists of time anyway, but hydrogen was most likely discovered when early chemists/alchemists noted the gas being formed when metals were treated with acids. They'd have found that it burned in air to form water.

Answer 2

Hydrogen was discovered in 1766 by English chemist Henry Cavendish. He collected and identified it as a gas produced during the reaction of metals with acids. Cavendish is credited with recognizing hydrogen as a distinct element.