Name the physicist who first measured the charge on an electron experimentally

The physicist who first measured the charge on an electron experimentally was Robert A. Millikan. In 1909, Millikan conducted his famous oil drop experiment, in which he observed tiny oil droplets suspended in an electric field. By balancing the gravitational force and the electric force acting on the droplets, Millikan was able to determine the charge on individual oil droplets. From these measurements, he could calculate the fundamental charge of an electron.