This book constitutes the refereed proceedings of the 13th International Conference on Reversible Computation, RC 2021, which was held online during July 7-8, 2021. The 11 papers included in this book were carefully reviewed and selected from 21 submissions. The book also contains 2 invited talks in full-paper length, 3 work-in-progress papers and 1 tool paper. They were organized in topical sections named: programming and programming languages; reversible concurrent computation; theory and foundations; and circuit synthesis.