This book constitutes the proceeding of the 26th International Conference on Automated Deduction, CADE-26, held in Gothenburg, Sweden, in August 2017. The 26 full papers and 5 system descriptions presented were carefully reviewed and selected from 69 submissions. CADE is the major forum for the presentation of research in all aspects of automated deduction, including foundations, applications, implementations and practical experience. The chapter 'Certifying Confluence of Quasi-Decreasing Strongly Deterministic Conditional Term Rewrite Systems' is published open access under a CC BY 4.0 license.