This book constitutes the proceedings of the 25th International Conference on Descriptional Complexity of Format Systems, DCFS 2023, which took place in Potsdam, Germany, in July 2023.The 14 full papers, including one invited presentation as a full paper, presented in this volume were carefully reviewed and selected from 16 submissions. The conference focus on all aspects of descriptional complexity, including automata, grammars, languages, and other formal systems; various modes of operations and complexity measures.