This book constitutes the refereed proceedings of the 26th IFIP WG 6.1 International Conference on Distributed Applications and Interoperable Systems, DAIS 2026, held in Urbino, Italy, during June 8-12, 2026, as part of the 21st International Federated Conference on Distributed Computing Techniques, DisCoTec 2026. The 7 full papers included in the proceedings were carefully reviewed and selected from 17 submissions. They were organized in topical sections as follows: Distributed Machine Learning and Storage and Distributed Systems.