This book constitutes the proceedings of the 26th International Workshop on Formal Methods for Industrial Critical Systems, FMICS 2021, which was held during August 24-26, 2021. The conference was planned to take place in Pairs, France. Due to the COVID-19 pandemic it changed to a virtual event.

The 10 full papers and 6 short papers presented in this volume were carefully reviewed and selected from 31 submissions. The papers are organized in topical sections as follows: Verification, Program Safety and Education, (Event-)B Modeling and Validation, Formal Analysis, Tools, Test Generation and Probabilistic Verification.