This book constitutes the proceedings of the 23rd International Conference on Unconventional Computation and Natural Computation, UCNC 2026, held in Trieste, Italy, during June 22-26, 2026.

The 16 full papers and 2 short papers presented in this volume were carefully reviewed and selected from 32 submissions. The UCNC series of international conferences is a forum bringing together scientists from many different backgrounds who are united in their interest in novel forms of computation, human-designed computation inspired by nature and computational aspects of natural processes.