English physicist.

Thomson studied engineering at Owen's College, Manchester, then in 1876 won a scholarship to Trinity College, Cambridge, where he graduated in mathematics in 1880. He remained at Cambridge University for the rest of his life, becoming Cavendish Professor of Experimental Physics in 1884.

Thomson is best known for his discovery of the electron in 1897 and for his investigation into its charge and mass. He also developed a mathematical theory of electricity and magnetism, and in 1906 was awarded the Nobel Prize for Physics for his research into the electrical conductivity of gases. In 1912 he proved the existence of isotopes of neon. He was responsible for establishing the Cavendish Laboratory as a leading research centre for subatomic physics.

Thomson's works include Elements of the Mathematical Theory of Electricity and Magnetism (1895) and Conduction of Electricity through Gases (1903). He received a knighthood in 1908. From 1915 to 1920 he served as President of the Royal Society and in 1918 was elected Master of Trinity College, a post he held until he died.