Felix Ehrenhaft (April 24, 1879 March 4, 1952) was an Austrian physicist who contributed to atomic physics, to the measurement of electrical charges and to the optical properties of metal colloids. He was known for his maverick and controversial style. His fearless iconoclasm was greatly admired by philosopher Paul Feyerabend.Ehrenhaft was born in Vienna to physician Leopold Ehrenhaft and Louise Eggar, the daughter of an Hungarian industrialist. Ehrenhaft earned his doctorate from the University of Vienna in 1903, working on the optical properties of metallic colloids. He subsequently became assistant to Viktor von Lang.