The 20th International Conference on Quantum Physics and Logic (QPL 2023) will take place from 17 July to 21 July 2023 at Institut Henri Poincaré in Paris, France. Quantum Physics and Logic is an annual conference that brings together academic and industry researchers working on mathematical foundations of quantum computation, quantum physics, and related areas. The main focus is on the use of algebraic and categorical structures, formal languages, type systems, semantic methods, as well as other mathematical and computer scientific techniques applicable to the study of physical systems, physical processes, and their composition. Work applying quantum-inspired techniques and structures to other fields (such as linguistics, artificial intelligence, and causality) is also welcome.