This volume constitutes the proceedings of the 26th International Conference on Web Services, ICWS 2019, held as part of SCF 2019 in San Diego, CA, USA in June 2019. The 11 full papers together with 1 short paper published in this volume were carefully reviewed and selected from 31 submissions. ICWS has been a prime international forum for both researchers and industry practitioners to exchange the latest fundamental advances in the state of the art and practice of Web-based services, to identify emerging research topics, and to define the future of Web-based services. Topics include Internet services modeling, discovery, composition, testing, adaptation, delivery, as well as standards.