Alexander (Alekos) Sotirios Kechris (Greek: Αλέξανδρος Σωτήριος Κεχρής; born March 23, 1946) is a descriptive set theorist and ergodic theorist at California Institute of Technology. He has made major contributions to the theory of Borel equivalence relations and the theory of automorphism groups of uncountable structures.
Kechris earned his Ph.D. in 1972 under the direction of Yiannis N. Moschovakis, with a dissertation titled Projective Ordinals and Countable Analytic Sets.
In 2012 he became a fellow of the American Mathematical Society.
- A. S. Kechris, "Classical Descriptive Set Theory", Springer-Verlag, 1995.
- H. Becker, A. S. Kechris, "The descriptive set theory of Polish group actions" (London Mathematical Society Lecture Note Series), University of Cambridge, 1996.
- A.S. Kechris, V.G. Pestov and S. Todorcevic, "Fraïssé limits, Ramsey theory and topological dynamics of automorphism groups", Geometric and Functional Analysis 15 (1) (2005), 106-189.
- A.S. Kechris, "Global Aspects of Ergodic Group Actions", Mathematical Surveys and Monographs, 160, American Mathematical Society, 2010.