The open access book set LNCS 16501 + LNCS 16502 constitutes the proceedings of the 35th European Symposium on Programming, ESOP 2026, which was held as part of the International Joint Conferences on Theory and Practice of Software, ETAPS 2026, in Turin, Italy, during April 11-16, 2026. The 31 full papers included in the proceedings, together with one invited talk, were carefully reviewed and selected from 94 submissions. They deal with fundamental issues in the specification, design, analysis and implementation of programming languages and systems, such as programming paradigms and styles; methods and tools to write and specify programs and languages; methods and tools for reasoning about programs; programming systems design and implementation.