Constantin Carathéodory (Greek: ???sta?t???? ?a?a?e?d??? Konstantinos Karatheodori; 13 September 1873 – 2 February 1950) was a Greek mathematician who spent most of his professional career in Germany.
He made significant contributions to the theory of functions of a real variable, the calculus of variations, and measure theory.
His work also includes important results in conformal representations and in the theory of boundary correspondence.
In 1909, Carathéodory pioneered the Axiomatic Formulation of Thermodynamics along a purely geometrical approach.