Professor Ong's research is broad, ranging across semantics of computation, programming languages,verification, logic and algorithms, and algorithmic game theory. A notable feature of his work is thecombination of ideas and methods from semantics and structures, with techniques from automated verification. Professor Ong is one of the leading figures and inventors of game semantics and its applications. His solution (with Hyland) to the PCF Full Abstraction Problem opened up the field of game semantics; and their constructions, known as Hyland-Ong games, have become standard notions in the semantics of programming languages. Professor Ong is also known for his pioneering contribution in the field of verification: his LICS 2006 paper co-initiated higher-order model checking, a new branch of algorithmic verification that combines ideas and methods from semantics with automata-theoretic and allied techniques in automatic verification, with applications to the verification of higher-order programs. His current research interests include computer and cyber security, higher-order logic and satisfiability modulo theories, and probabilistic and differentiable programming. Throughout his long stay in Oxford, Professor Ong has supervised well over 60 doctoral students and postdocs.