This book constitutes the proceedings of the 26th International Conference on Automated Reasoning with Analytics Tableaux and Related Methods, TABLEAUX 2017, held in Brasilia, Bazil, in September 2017.

The 19 papers presented in this volume were carefully reviewed and selected from 27 submissions. They were organized in topical sections named: Sequents systems; tableaux; transitive closure and cyclic proofs; formalization and complexity.