Who discovered hydrogen?
In the 16th century the wellknown alchemist Paracelsus knew
something about this gas.
In 1671, Robert Boyle discovered and described the reaction between iron filings and dilute acids, which results in the production of a gas.
In 1766 Henry Cavendish recognized this gas as a different substance; he named this gas "flammable air".
The name hydrogen is from Antoine Lavoisier, in 1783.
Now Cavendish is credited with the discovery of hydrogen but the history is long and complicated.
For the history of hydrogen see the link below.