This book constitutes the refereed proceedings of the 18th International Conference on Logic Programming and Nonmonotonic Reasoning, LPNMR 2026, held in Klagenfurt, Austria, during September 7–11, 2026.

The 28 full papers and 4 short papers included in this book were carefully reviewed and selected from 46 submissions. The papers presented at the conference covered various topics focusing on design and
implementation of logic-based programming languages and database systems, as well as knowledge representation and non-monotonic reasoning.