This book constitutes the proceedings of the 47th International Workshop on Graph-Theoretic Concepts in Computer Science which was held during June 23–25, 2021. The conference was planned to take place in Warsaw, Poland, but changed to an online event due to the COVID-19 pandemic. The 30 full papers included in this volume were carefully reviewed and selected from 73 submissions. The conference aims to merge theory and practice by demonstrating how concepts from graph theory can be applied to various areas in computer science or by extracting new graph-theoretic  problems from applications.Chapter “Bears with Hats and Independence Polynomials” is are available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.Chapters 1, 6, and 22 are available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.