Isabelle Stone (1868–1944) was an American physicist and one of the founders of the American Physical Society. She was the first woman to be awarded a PhD in physics in the United States.
Stone was born in 1868 to Harriet and Leander Stone in Chicago. She attended Wellesley College and Columbia University from which she received her degrees, and taught at Bryn Mawr School and Vassar College. She was the first woman to gain a PhD in physics the United States and did so at the University of Chicago.
Stone was, out of a total of 836, one of two women who attended the first International Congress of Physics in Paris (the other being Marie Curie).
The exact date of her death is unknown.
Stone's research was on the electrical resistance and other properties of thin films. Her thesis, On the Electrical Resistance of Thin Films, showed that very thin metal films showed a higher resistivity than the bulk metal.