This book constitutes the refereed proceedings of the 25th IFIP WG 6.1 International Conference on Distributed Applications and Interoperable Systems, DAIS 2025, held in Lille, France, as Part of the 20th International Federated Conference on Distributed Computing Techniques, DisCoTec 2025, during June 16–20, 2025.The 7 full papers included in this book were carefully reviewed and selected from 16 submissions.They focus on all practical and conceptual aspects of distributed applications, including their design, modeling, implementation, and operation; the supporting middleware; appropriate software engineering methodologies and tools; and experimental studies and applications.