Luca Cardelli is distinguished for his innovative work on the theory and implementation of programming languages, extending to mathematical modelling of interactive and mobile systems. His early compiler for the ML language was crucial for its adoption by a wide community. As a leading designer of the language Modula-3, he advanced the understanding of modular structure for programming. He has made many contributions to type theory in computing, notably in subtyping, polymorphism and applications to inheritance. A series of papers with Martin Abadi, culminating in a book, constitute the deepest theoretical study there has so far been of object-oriented computing. His mobile ambients, involving a novel spatiotemporal modal logic, offer a model for modern mobile computation which provides an elegant conceptual basis for the rigorous analysis of systems up to the scale of the World Wide Web. His theoretical work is informed by his sharp appreciation of the architectural and security issues concerning migratory and distributed systems. In recent years, he has integrated computational techniques in the study of structural DNA nanotechnology and molecular biology.