This book constitutes the refereed post-conference proceedings of the 20th International Conference, LENLS20, held in Osaka, Japan, during November 18-20, 2023.The 19 full papers presented were carefully reviewed and selected from 46 submissions. The conference aims to cover the topics at the Intersection of Language and logic, and so Centers Around Linguistics, both Theoretical and Computational; Logic; Philosophy; and other sorts of Formal Approaches to these topics such as Game Theory.