Whose discovery first established hydrogen as a separate element from air and phlogiston-era chemistry?

Henry Cavendish identified hydrogen in 1766 as a distinct substance he called “inflammable air.” He studied its properties carefully and showed that burning it produced water, overturning older ideas about the composition of air and water. Later the gas was named hydrogen, meaning water-former. Cavendish’s work helped lay the groundwork for modern chemical analysis and the idea that water is a compound, not an element. Hydrogen later became the first element in the periodic table by atomic number.