This book constitutes the refereed proceedings of the 42nd German Conference on Artificial Intelligence, KI 2019, held in Kassel, Germany, in September 2019.

The 16 full and 10 short papers presented together with 3 extended abstracts in this volume were carefully reviewed and selected from 82 submissions.

KI 2019 has a special focus theme on "AI methods for Argumentation" and especially invited contributions that use methods from all areas of AI to understand, formalize or generate argument structures in natural language.