Ehud Kalai is a prominent American game theorist and mathematical economist known for his contributions to game theory and its interface with economics, social choice, computer science and operations research. 

In cooperative game theory, the Kalai-Smorodinsky solution reopened the study of bargaining by showing that the long unchallenged Nash solution is not unique. He later axiomatized the Egalitarian solution to bargaining problems and, with D. Samet, formulated its extension to general (NTU) cooperative games, unifying it with the Shapley (TU) Value. In non cooperative game theory, the Kalai-Lehrer model of rational learning showed that rational players with truth-compatible beliefs eventually learn to play Nash equilibria of repeated games. In particular, in Bayesian equilibria of repeated games all relevant private information eventually becomes common knowledge. Kalai's work on large games showed that the equilibria of Bayesian games with many players are structurally robust, thus large games escape major pitfalls in game-theoretic modeling.

Kalair is also known for seminal collaborative research on flow games and totally balanced games; strategic complexity and its implications in economics and political systems; arbitration, strategic delegation and commitments; extensions of Arrow's Impossibility Theorem in social choice; competitive service speed in queues; and on rational strategic polarization in group decision making.