This book constitutes revised selected papers from the 12th International Workshop on Rewriting Logic and Its Applications, WRLA 2018, held in Thessaloniki, Greece, in June 2018. The 12 full papers presented in this volume were carefully reviewed and selected from 21 submissions. They deal with rewriting, a natural model of computation and an expressive semantic framework for concurrency, parallelism, communication, and interaction, and its applications.