The proton was discovered by Ernest Rutherford. He identified the proton as a fundamental subatomic particle in 1917 during experiments where he bombarded nitrogen gas with alpha particles and observed the emission of positively charged hydrogen nuclei, which he named protons. This discovery was a major advancement in atomic theory, showing that protons are constituents of atomic nuclei in all elements except hydrogen, whose nucleus is a single proton.
Although Eugen Goldstein discovered canal rays (positively charged ions) earlier in 1886, and these canal rays included hydrogen ions, it was Rutherford who demonstrated that hydrogen nuclei (protons) are actual subatomic particles within atoms.
Thus, Rutherford is credited with the discovery of the proton as a nuclear particle.
