The discovery of the electron is credited to J.J. Thomson in 1897. He conducted experiments with cathode rays and determined that they were made up of particles much smaller than atoms, which he named electrons.

Julius Plücker, a German physicist, did important work in the 19th century on cathode rays and the properties of gas discharges. His work laid the groundwork for Thomson's later discovery. However, he did not identify the electron itself.