This book constitutes the refereed proceedings of the 11th International Symposium on Dependable Software Engineering. Theories, Tools, and Applications, SETTA 2025, held in Oxford, UK, during December 1–3, 2025.The 18 full papers and 1 invited paper presented in this volume were carefully reviewed and selected from 46 submissions. The papers are organized in the following topical sections: Invited Contribution; Software Quality and System Design; Logic and Theorem Proving; Automata; Monitoring; Formal Verification; Neural Networks and Large Language Models; Blockchains and Distributed Protocols.