This book constitutes the refereed proceedings of the 21st Conference of the Spanish Association for Artificial Intelligence, CAEPIA 2026, held in Jaén, Spain, during November 11-13, 2026.

The 38 full papers presented in this book were carefully reviewed and selected from 182 submissions. The papers covers such themes as computer vision and robotics; foundational models / LLMs; machine learning; optimization, search and planning; real-world applications; and recommender systems.